Special libraries, as differentiated from general public libraries and academic libraries, are devoted to specialized fields of science and technology, agriculture, medicine, social sciences, economics and the like. Such libraries are attached to research organizations, government departments, departments in universities, industrial organizations, professional societies and trade associations, etc. Special libraries customarily maintain a regular and systematic information service covering the immediate and future interests of the organizations of which they are part. This necessitates the development and management of an adequate collection of books, periodicals, reports, patents, standards, government publications, maps, audio-visual records, etc. issuing from a multitude of publishing bodies. In house publications, market surveys, data files, etc. are also brought together in these collections. All items are of course made available for consultation by being adequately classified or indexed and organised in a particular fashion and maintained for future reference.