g33~ 0 , for S O ~ SU~ ~ S P 2 , for S02.1~ S U I , I ~ S L ~ , ~ SP2,~ , ~er E~. The group E2, describing the three-parameter Euclidean algebra in two dimensions is of no importance for the further discussion and will be omitted in the rest of the paper. Let us consider the vector products of the form (3) [ [ L x L ] (k) x [/-, x L](*)] (~ , where ~5 is a vector with spherical components J5~1, L0 defined by (1) and (2). The components of the vector product are given by