British Library Document Supply Centre Research Articles

British Library document supply – a fork in the road

PurposeThis paper seeks to provide an overview of recent developments within the British Library's document supply service and offer an insight into future plans.Design/methodology/approachThe paper takes the form of a general review.FindingsThe British Library Document Supply Centre (BLDSC) has made tremendous gains in optimising the service in its current guise. As with similar organisations, challenges are presenting themselves that require a completely new look at the way the business model is designed. Although the long‐term plan is not completely formed, this paper aims to give an insight into current thinking.Originality/valueThe paper spells out the improvement strategy that the BL has adopted for document supply in the light of the worldwide decline.

Donald J. Urquhart and the integration of science with librarianship: Part 2

PurposeTo analyze the historical significance of Donald J. Urquhart, who established the National Lending Library for Science and Technology (NLL) which later was merged into the British Library Lending Division (BLLD), now called the British Library Document Supply Centre (BLDSC). His significance will be considered from the perspective of the development of science as a whole as well as library and information science in particular.Design/methodology/approachThe paper presents a short history of the probabilistic revolution, particularly as it developed in Britain in the form of biometric statistics due to Darwin's theory of evolution. It focuses on the overthrow of the normal paradigm, according to which frequency distributions in nature and society conform to the normal law of error. The paper discusses the importance of the Poisson distribution and its utilization in the construction of stochastic models that better describe reality. Here the focus is on the compound Poisson distribution in the form of the negative binomial distribution (NBD). The paper then shows how Urquhart extended the probabilistic revolution to librarianship by using the Poisson as the probabilistic model in his analyses of the 1956 external loans made by the Science Museum Library (SML) as well as in his management of the scientific and technical (sci/tech) journal collection of the NLL. Due to this, Urquhart can be considered as playing a pivotal role in the creation of bibliometrics or the statistical bases of modern library and information science. The paper relates how Urquhart's son and daughter‐in‐law, John A. and Norma C. Urquhart, completed Urquhart's probabilistic breakthrough by advancing for the first time the NBD as the model for library use in a study done at the University of Newcastle upon Tyne, connecting bibliometrics with biometrics. It concludes with a discussion of Urquhart's Law and its probabilistic implications for the use of sci/tech journals in a library system.FindingsBy being the first librarian to apply probability to the analysis of sci/tech journal use, Urquhart was instrumental in the creation of modern library and information science. His findings force a probabilistic re‐conceptualization of sci/tech journal use in a library system that has great implications for the transition of sci/tech journals from locally held paper copies to shared electronic databases.Originality/valueThis is the second part of an article describing the seminal contribution of Donald Urquhart to the development of document supply in the UK and internationally.

Donald J. Urquhart and the integration of science with librarianship: Part 1

PurposeThe purpose of this article is to analyze the historical significance of Donald J. Urquhart, who established the National Lending Library for Science and Technology (NLL) that later was merged into the British Library Lending Division (BLLD), now called the British Library Document Supply Centre (BLDSC).Design/methodology/approachThe paper presents a short history of the probabilistic revolution, particularly as it developed in the UK in the form of biometric statistics due to Darwin's theory of evolution. It focuses on the overthrow of the normal paradigm, according to which frequency distributions in nature and society conform to the normal law of error. The paper discusses the importance of the Poisson distribution and its utilization in the construction of stochastic models that better describe reality. Here the focus is on the compound Poisson distribution in the form of the negative binomial distribution (NBD). The paper then shows how Urquhart extended the probabilistic revolution to librarianship by using the Poisson as the probabilistic model in his analyses of the 1956 external loans made by the Science Museum Library (SML) as well as in his management of the scientific and technical (sci/tech) journal collection of the NLL. Thanks to this, Urquhart can be considered as playing a pivotal role in the creation of bibliometrics or the statistical bases of modern library and information science. The paper relates how Urquhart's son and daughter‐in‐law, John A. and Norma C. Urquhart, completed Urquhart's probabilistic breakthrough by advancing for the first time the NBD as the model for library use in a study executed at the University of Newcastle upon Tyne, connecting bibliometrics with biometrics. It concludes with a discussion of Urquhart's Law and its probabilistic implications for the use of sci/tech journals in a library system.FindingsBy being the first librarian to apply probability to the analysis of sci/tech journal use, Urquhart was instrumental in the creation of modern library and information science. His findings force a probabilistic re‐conceptualization of sci/tech journal use in a library system that has great implications for the transition of sci/tech journals from locally held paper copies to shared electronic databases.Originality/valueUrquhart's significance is considered from the perspective of the development of science as a whole as well as library and information science in particular.

Urquhart and probability: The transition from librarianship to library and information science

AbstractIn this article, I analyze the role of Donald J. Urquhart in the creation of modern library and information science. Urquhart was one of the chief architects of information science in Britain and founder of the National Lending Library for Science and Technology (NLL), which evolved into the present‐day British Library Document Supply Centre (BLDSC). In particular, I focus on the part played by Urquhart in the development of that branch of information science termed bibliometrics, the application of mathematical and statistical techniques to information phenomena, pursuing both historical and practical aims. The article is intended not only to trace the history of the probability distributions applicable to library use and other facets of human knowledge but also to demonstrate how these distributions can be used in the evaluation and management of scientific journal collections. For these purposes, the paper is divided into three parts of equal importance. The first part is statistical and establishes the theoretical framework, within which Urquhart's work is considered. It traces the historical development of the applicable probability distributions, discussing their origins on the European continent and how Continental principles became incorporated in the biometric statistics that arose in Britain as a result of the Darwinian revolution. This part analyzes the binomial and Poisson processes, laying out the reasons why the Poisson process is more suitable for modeling information phenomena. In doing so, it describes key distributions arising from these processes as well as the various tests for these distributions, citing the literature that shows how to conduct these tests. Throughout the discussion, the relationship of these distributions to library use and the laws of information science is emphasized. The second part of the article analyzes the pioneering role of Urquhart as a conduit for the entry of these probability distributions into librarianship, converting it into library and information science. He was the first librarian to apply probability to library use, utilizing it not only to establish and manage the scientific journal collections of the NLL but also to evolve his Law of Supralibrary Use. Urquhart's work is portrayed within the context of a general trend to adopt probabilistic methods for analytical purposes, and a major premise of this article is that his law and the probabilistic breakthrough, on which it was based, were most likely in Britain, which was one of the few countries not only to develop but also maintain the necessary scientific preconditions. The third—and concluding section—discusses how Urquhart's Law forces a probabilistic reconceptualization of the functioning of the scientific journal system as well as the law's practical implications for journal sales, collection evaluation and management, resource sharing, and the transition from the paper to the electronic format.

Monograph Interlending for the Higher Education Research Community

1. This report was commissioned by CURL (the Consortium of University Research Libraries) with the support of the British Library Cooperation and Partnership Programme in order to recommend the best UK wide monograph interlending infrastructure and associated business model for the higher education research community for the next ten years. The report does not consider the interlending needs of other sectors (for example, public libraries), but its recommendations are unlikely to have adverse implications for them. 2. The report estimates that for 2001-2002 the overall total of interlending requests initiated by the UK higher education sector was approximately 325,000. Of these some 90% (295,000) were estimated to have been successfully completed, of which approximately 79% were supplied by the British Library Document Supply Centre (BLDSC), which holds the most dominant position in the UK monograph interlending system. In addition to the BLDSC there are a number of other providers to whom higher education libraries typically turn if the BLDSC cannot supply an item, but the overall volume of such loans is low. 3. The current monograph interlending system based on the BLDSC has several important strengths: first and most importantly, it works, and has done so successfully for many years. The system is well understood by researchers, is valued by them, and as our own data demonstrates has the support of all CURL libraries. The overall performance of the BLDSC is high in terms of speed of delivery and other operational benchmarks, and also represents good value for money for the sector as a whole. Studies undertaken for the Research Support Libraries Group (RSLG) estimated the savings achieved through all forms of central document supply to be between £45 and £50 million. In relation to individual loan charges an email survey of CURL libraries suggested that although those responding welcomed the cheaper options provided by some other providers, the charges of the BLDSC were accepted as being at least satisfactory. 4. The current system has no major weaknesses, however significant concerns exist about whether it can be sustained in the future without change. The current interlending system is likely to come under increasing strain because of: declining investment in loan stock unless more collaborative approaches to acquisition take place; an increase in the diversity of lending provision as libraries struggle to meet the needs of their own researchers in the context of a declining central fill rate; and specific difficulties concerning the loan of items from special collections. These concerns are part of the broader issue of the future of library resources which is addressed in the RSLG report. 5. If such developments were allowed to occur, they would lead to the loss of many of the advantages of centralisation that now exist, and involve interlending librarians spending much more time trying to source material. Rather we see the opposite as desirable: obtaining maximum benefit through a suitably run single source of supply, with as much requesting and distribution as possible done electronically. The RSLG has made it clear that a gradual deterioration in resource availability for research use should not be accepted, and our conclusion is that the same principle should apply to document supply and loans. 6. The report considers nine wide-ranging options for revising the current interlending system, and seeks to build upon existing strengths. Each option is tested against six key criteria: ○ It should enable the current fill rate in higher education libraries of approximately 90% to be maintained, and if possible improved. ○ It should operate to performance standards not lower than those currently achieved by the BLDSC. ○ It should maximise value for money in relation to collection development, procurement, and in other related areas.

Is this the end of the “article economy”? A strategic review of document delivery

With the advent of the Internet, the Web and electronic publishing systems, new ways of delivering scholarly information have arisen which challenge some of the traditional growth assumptions made for document delivery. Conventional theory described an emerging need for an escape valve to release some of the tensions created by institutional budgets being unable to keep track with the growing output and price escalation of published information. Document delivery and its cousin, interlibrary loan, provided such a release mechanism. However, it is apparent that information technology (IT) is providing new ways to overcome the traditional “frustration gap” between document demand and supply. These new options pose both a challenge and an opportunity for the British Library Document Supply Centre (BLDSC) which remains the world's largest document delivery agency. The article will discuss some of the ways BLDSC is adapting in order to retain its leadership role and remain in tune with new end user demands for information.

Delivering Agricultural Documents: A Comparison of Suppliers

ABSTRACT Academic communication and discourse requires access to scientific journals and documents. This study examines the delivery time, costs, and quality of five commercial suppliers of scientific documents. Fifty-three agricultural article requests were ordered simultaneously from The British Library Document Supply Centre (BLDSC), The Canadian Institute of Scientific and Technical Information (CISTI), Information Express (IE), Infotrieve (INFO), UnCover (UNCOVER). Data were gathered on each supplier's performance in filling the requests, the delivery time, the costs, and the quality of the articles supplied. The results of this study showed comparative strengths and limitations. BLDSC, CISTI, and IE were all similar, consistently delivering high quality documents. INFO alone was able to deliver all 53 requested articles. UNCOVER showed two strengths, delivering the requested documents quickly and replying back if the article order was cancelled.

Bridging the Gap Inside … Inside Document Delivery

Librarians today are faced with many choices when acquiring information and directing their users to the sources they need. This is most evident with serials. The choices have become more confusing with new options requiring libraries to determine what a full text purchase actually buys, how to be sure users can identify the material needed, and then how to acquire the actual material in the most appropriate media. Providing access by the piece is a valid solution that can help lead to the transition to full text online journals. This article critiques the use of the British Library Document Supply Centre's “inside” service and its use at the University of Illinois at Urbana-Champaign Library (UIUC). The article concludes with a review of the components of a good document delivery system.

British Library Document Supply Centre uses OCLC IFM service

British Library Document Supply Centre uses OCLC IFM service

Urquhart's and Garfield's Laws: The British controversy over their validity

AbstractThe British controversy over the validity of Urquhart's and Garfield's Laws during the 1970s constitutes an important episode in the formulation of the probability structure of human knowledge. This controversy took place within the historical context of the convergence of two scientific revolutions—the bibliometric and the biometric—that had been launched in Britain. The preceding decades had witnessed major breakthroughs in understanding the probability distributions underlying the use of human knowledge. Two of the most important of these breakthroughs were the laws posited by Donald J. Urquhart and Eugene Garfield, who played major roles in establishing the institutional bases of the bibliometric revolution. For his part, Urquhart began his realization of S. C. Bradford's concept of a national science library by analyzing the borrowing of journals on interlibrary loan from the Science Museum Library in 1956. He found that 10% of the journals accounted for 80% of the loans and formulated Urquhart's Law, by which the interlibrary use of a journal is a measure of its total use. This law underlay the operations of the National Lending Library for Science and Technology (NLLST), which Urquhart founded. The NLLST became the British Library Lending Division (BLLD) and ultimately the British Library Document Supply Centre (BLDSC). In contrast, Garfield did a study of 1969 journal citations as part of the process of creating the Science Citation Index (SCI), formulating his Law of Concentration, by which the bulk of the information needs in science can be satisfied by a relatively small, multidisciplinary core of journals. This law became the operational principle of the Institute for Scientific Information created by Garfield. A study at the BLLD under Urquhart's successor, Maurice B. Line, found low correlations of NLLST use with SCI citations, and publication of this study started a major controversy, during which both laws were called into question. The study was based on the faulty use of the Spearman rank‐correlation coefficient, and the controversy over it was instrumental in causing B. C. Brookes to investigate bibliometric laws as probabilistic phenomena and begin to link the bibliometric with the biometric revolution. This paper concludes with a resolution of the controversy by means of a statistical technique that incorporates Brookes' criticism of the Spearman rank‐correlation method and demonstrates the mutual supportiveness of the two laws.

Using local citation data to relate the use of journal articles by academic researchers to the coverage of full‐text document access systems

The methodology and findings are presented of an empirical study comparing local citation patterns with the holdings lists of a number of sources of journal articles. These sources were the British Library Document Supply Centre (BLDSC) and the BL inside service, library holdings, ProQuest Direct, SearchBank, EiText and a linking system including both the Geobase database and the BLDSC. The value of local citation figures is discussed, as is the concept of a “core” of journal titles, from both theoretical and practical perspectives. Using these figures to represent the local use of journal articles, the coverage of the document sources was found to vary widely. Unsurprisingly, the BLDSC was found to offer the widest coverage. Newer, electronic systems generally fared less well, but may offer other advantages.

Book Reviews

A. Morris, N. Jacobs, E. Davies Document delivery beyond 2000. Proceedings of a conference held at the British Library, September 1998 (eds). London : Taylor Graham , 1999 . ISBN 947568 76 X . 188 pp., £30.00 [paperback]. A. Morris, N. Jacobs and E. Davies (eds). London: Taylor Graham, 1999. ISBN 947568 76 X. 188 pp., £30.00 [paperback]. Librarians and information professionals everywhere subscribe to the view that no library is self-sufficient and that we rely on co-operative action in order to meet our users’ needs. Document delivery is central to this interdependence, and it is thus unsurprising that technological advances—notably in the electronic transmission of text and graphics—should be receiving so much attention today. Paradoxically, however, the same technology that enables us institutionally to communicate more efficiently on behalf of our users also increasingly offers those end-users the means of bypassing our institutional information services and of obtaining what they need by direct recourse to publishers and other information suppliers. This conference, sponsored by the Joint Information Systems Committee (JISC) of the UK Higher Education Funding Councils as part of its Electronic Libraries Programme (eLIB), is thus a timely contribution to a debate that has no clear end in sight. Despite its UK and higher education origins, the conference was international in scope, and dealt with topics that are relevant to any librarian dealing with the changing nature of document delivery technology and the need to develop services accordingly. This includes the many health-care librarians working within networks and consortia that offer internal document delivery services as one of their main operational justifications. The conference programme was actually planned with the aid of an e-mail discussion that allowed interested parties to identify themes they wished to see explored. It gave rise to a programme in two phases: the ‘role-focused view’ concentrated on the people involved in the document delivery process, while the ‘infrastructure-focused view’ examined the requirements of the process. The conference proceedings reflect this structure, with 17 papers in two clusters, each followed by a series of short reports from the break-out sessions that developed delegate participation. In the UK—and to a considerable extent internationally—it remains the case that the document delivery market is dominated by the British Library Document Supply Centre (BLDSC), which provided several of the conference speakers. Some of the other contributions here, describing services and products such as LAMDA, EDDIS and ARIEL and other popular buzz-acronyms, might be seen as developments that challenge the predominance of the BLDSC, offering librarians alternative organizational and technological approaches. Inevitably, the focus of attention is the advent of electronic technologies and their potential for streamlining existing delivery channels. It is indeed still the case that most library users require information sources that exist in print form. The BLDSC model of a repository holding stock that can be copied and delivered elsewhere quickly, reliably and cheaply—and its network equivalent, where the repository is the aggregate resources of a co-ordinated group of libraries—will thus continue to occupy centre stage for a while even in the sciences, and for longer in the arts and humanities. This volume of conference papers provides a useful and thought-provoking summary of the options that are available for library services wishing to be aware of the possibilities in document delivery, and explores very thoroughly the organizational, technical and legal issues that need to be considered. However the real debate, not addressed here in any detail, will involve the imminent explosion in the number of full-text electronic journals available to users, and with it their ability to obtain downloaded copies of the articles they require. The consequences for library-based document delivery services are immense.

Digital Dissertations in the United Kingdom

In the United Kingdom a user wishing to consult a UK thesis has traditionally had the following choices: the thesis may be consulted in the Library of the Higher Education Institution (HEI) to which it was submitted; the thesis may be borrowed from the library of the HEI; a copy of the thesis may be purchased form the library of the HEI; the thesis may be borrowed through inter-library loan; or the thesis may be made available through the British Library’s British Thesis Service, which was set up in 1971. This Service currently holds more than 150,000 UK theses, which are added to at a rate of around 7,000 a year, with the participation of about a hundred Higher Education Institutions (HEIs). With the development of new technology, however, an interest developed in examining the feasibility of making theses available online to users. In the United Kingdom, the University Theses Online Group (UTOG) was established as a consequence of a proposal to the Follett Implementation Group on Information Technology in 1994. The University Theses Online Group (UTOG) is a working group of UK university librarians: the Group’s aims are to investigate the technical, cultural and administrative issues associated with the storage and delivery of theses in online form. The Group is made up of representatives of the British Library Document Supply Centre (BLDSC), British Thesis Service, and the university libraries of Cranfield, Edinburgh, Glasgow, Leeds, Manchester, Plymouth, Robert Gordon, University College London, Kent, University of London and Warwick.

Unmediated document delivery: a project using FirstSearch and EBSCOdoc

Staffing costs account for 65 per cent of research libraries’ expenditures for interlibrary borrowing. Due to this cost and pressure to provide better access, library administrators are showing an increased interest in unmediated document delivery. In a pilot project at Texas A&M University, faculty and graduate students in the Agricultural Economics Department used ArticleFirst, PapersFirst, and EBSCOdoc as a substitute for traditional interlibrary loan. Participants could order materials not owned by the three university libraries. Four document suppliers, the British Library Document Supply Centre, EBSCOdoc, ISI’s Genuine Article and UMI were used. Users were allowed to select the vendor and method of delivery which included fax, mail, Ariel, and express mail. Data gathered included the usage patterns for the different delivery methods and document suppliers, the costs of items, problems encountered by users, and general information on user satisfaction.

British Library Document Supply Centre to offer ILL rush service on OCLC requests

British Library Document Supply Centre to offer ILL rush service on OCLC requests

BLDSC Acquisitions from Eastern Europe

The changes in the politics and economics of the countries of Eastern and Central Europe have led to difficulties in the acquisition of printed material from those countries. The article outlines the current means employed by the British Library Document Supply Centre to obtain the items required by its readers and gives some opinions on the future of acquisitions from each of these countries, concluding that future acquisitions will rely much more heavily on purchasing than exchange.

Structure and topography of the membrane-binding C2 domain of factor VIII in the presence of dodecylphosphocholine micelles.

A 21 residue peptide from the C2 domain of the antihaemophilic factor VIII competes with factor VIII for membrane-binding sites in vitro. Here, we provide the structure and topography of the peptide in solution, on dodecylphosphocholine (DPC) micelles, determined using 1H-NMR spectroscopy. The peptide assumes an amphipathic structure comprising an extended N-terminal region and a C-terminal helix. The average root-mean-square deviation is 0.7+/-0.2 A for the superimposition of the backbone atoms of Ile6 to Arg18 on the lowest energy structure. Whereas the backbone conformation is similar to that in SDS micelles, the Trp11 side-chain orientation is dramatically changed. The indole ring is nearly parallel to the peptide backbone in SDS micelles but perpendicular in DPC micelles. Further, pKa values of the two histidines change by more than 1 pH unit in SDS relative to DPC, which localizes the imidazole rings to the interfacial region. Line-broadening induced by spin-labelled phosphatidylcholine shows that most of the amino acid side-chains that penetrate the DPC micelle are hydrophobic. Thus, the long axis of the peptide lies parallel to the micelle surface and the hydrophobic face of the alpha-helix provides hydrophobic membrane interaction. The large chemical shift changes shown by Trp11 and N-terminal amino acid residues in SDS relative to DPC indicate that this region may be involved in membrane phospholipid recognition. 1H-NMR assignments, CD spectra, one-dimensional 1H-NMR spectra, chemical-shift analysis and nuclear Overhauser effect information are reported in Supplementary Publication SUP 50184 (11 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K, from whom copies can be obtained according to the terms indicated in Biochem. J. (1997) 321, 8.

Why requests fail

Describes a study undertaken in 1996 to examine interlibrary loan and document supply request failures in the UK and Ireland. The project surveyed 54 public, university and special libraries, monitoring and categorizing their failed requests and their failures to supply items requested from them. Differences in rates and nature of request failure between libraries of different types and for different types of material were examined. Data were simultaneously collected on requests passing through the British Library Document Supply Centre, reply codes were monitored and analysed, and operational systems and procedures examined. Conclusions were drawn and recommendations made at a national policy level and at the operational, practice‐based level. At national level they include access strategies, acquisitions and retention policies, and resource discovery strategies. At operational level they focus on the submission of requests, the use, management and maintenance of databases and catalogues, and technical standards.

A Cost-Effectiveness Study of Ownership versus Access

This paper describes a method which was used to evaluate the cost-effectiveness of three different ways of supplying periodical articles in an academic library. The methods considered were: subscribing to a periodical title (ownership); individual article supply provided by two electronic document delivery services, Arti-clesFirst of OCLC FirstSearch and UnCover; and traditional article supply through the British Library Document Supply Centre. The operational costs of the alternatives are obtained by taking a management accounting approach and are examined in relation to the provision of the services within the library of St. Patrick's College, May-nooth, Ireland. The cost-per-use of owning a periodical title is calculated based on the operational costs of the Periodicals Department of the library, its subscription price and a lifetime use determined by examination of the current requests for articles made through the library's Inter-Library Loans Department. The cost-peruse for the other services are also calculated based on their operational costs and document delivery charges.

A mutant phosphofructokinase produces a futile cycle during gluconeogenesis in Escherichia coli.

Strains of Escherichia coli bearing different forms of phosphofructokinase were used to assess the occurrence of futile cycling in cell resuspensions supplied with glycerol as gluconeogenic carbon source. A model was used to simulate results of different kinds of experiments for different levels of futile cycle. The main predictions of the model were experimentally confirmed in a strain with a mutant phosphofructokinase-2 (phosphofructokinase-2*) which is not inhibited by MgATP. The intracellular fructose 1, 6-bisphosphate concentration reaches significantly higher levels in the mutant-bearing strain than in strains with either phosphofructokinase-1 or -2. Also, this strain showed a higher rate and level of in vivo radioactive labelling of fructose 1, 6-bisphosphate, from a trace of [U-14C]glucose supplied during gluconeogenesis, indicating higher kinase activity in these conditions. Cell resuspensions of the mutant-bearing strain produced higher levels of radioactively labelled CO2 when supplied with [U-14C]glycerol as the only carbon source. Simultaneously, fewer glycerol carbons were incorporated into HClO4-insoluble macromolecules. Finally, radioactive CO2 output was measured in resuspensions supplied with glycerol as the major carbon source with traces of either [1-14C]glucose or [6-14C]glucose. It was found that, whereas in the strains with either of the wild-type phosphofructokinase isoenzymes, radioactive CO2 output from [1-14C]glucose was higher than with [6-14C]glucose, the reverse is found for the strain with phosphofructokinase-2*. This result also agrees with the corresponding prediction of the model. Using the radioactivity flux rates predicted by the model, an explanation linking the futile cycle to the differential labelling of CO2 is advanced. Finally, on the basis of these results it is proposed that strains bearing phosphofructokinase-2* sustain higher rates of futile cycling during gluconeogenesis than strains bearing either of the wild-type isoforms of phosphofructokinase. The kinetic equations and parameter values used for the model simulations are given in Supplementary Publication SUP 50183 (8 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1997) 321, 8.