... Automatic classification of large catalogs may be carried out for survey objectives, or to elucidate the catalog's contents in a minimally-restricted way. ... 1992; Murtagh & Hern?ndez-Pajares 1994; Hern?ndez-Pajares et al. 1994): each item in a multidimensional input data set is assigned to a cluster center; the cluster centers are themselves ordered by their proximities; and the cluster centers are arranged in some specific output representational structure, often a regularly-spaced grid. ... 1994...