C. Lu, X. Chen, and E. Park. CIKM '09: Proceeding of the 18th ACM conference on Information and knowledge management, page 1545--1548. New York, NY, USA, ACM, (2009)
T. Yoshizawa. Recent developments in clustering and data analysis: Proceedings of the Japanese-French Scientific Seminar, March 24-26, 1987., Academic Press, Boston, (1988)
T. Wansbeek, and J. Buyze. Research Report BPA, 13593-81-M1. Department for Statistical Methods, Central Bureau of Statistics, Voorburg, The Netherlands, (1981)