1. J.D. Barrow, S.P. Bhavsar and D.H. Sonoda, “Minimal spanning trees, filaments and galaxy clustering”, Monthly Notices of the Royal Astronomical Society, 216, 17–35, 1985. (This article follows the seminal approach of Zahn — see reference among the general clustering works — in using the MST for finding visually evident grou pings.)
2. R. Bianchi, A. Coradini and M. Fulchignoni, “The statistical approach to the study of planetary surfaces”, The Moon and the Planets, 22, 293–304, 1980. (This article contains a general discussion which compares the so-called G-mode clustering method to other multivariate statistical methods. References 7 and 8 below also use this method.)
3. R. Bianchi, J.C. Butler, A. Coradini and A.I. Gavrishin, “A classification of lunar rock and glass samples using the G-mode central method”, The Moon and the Planets, 22, 305–322, 1980.
4. A. Bijaoui, “Méthodes mathématiques pour la classification stellaire”, in Classification Stellaire, Compte Rendu de l’Ecole de Goutelas, ed. D. Ballereau, Observatoire de Meudon, Meudon, 1979, pp. 1–54. (This presents a survey of clustering methods.)
5. R. Buccheri, P. Coffaro, G. Colomba, V. Di Gesù and S. Salemi, “Search of significant features in a direct non-parametric pattern recognition method. Application to the classification of multiwire spark chamber pictures”, in (eds.) C. de Jager and H. Nieuwenhuijzen, Image Processing Techniques in Astronomy, D. Reidel, Dordrecht, pp. 397–402, 1975. (A technique is developed for classifying I-ray data.)