A. Weingessel, E. Dimitriadou, und S. Dolnicar. Working Paper 29. SFB ``Adaptive Information Systems and Modeling in Economics and Management Science'', (1999)
G. Salton, und C. Buckley. SIGIR '88: Proceedings of the 11th annual international ACM SIGIR conference on Research and development in information retrieval, Seite 147--160. New York, NY, USA, ACM Press, (1988)
J. Bezdek, W. Li, Y. Attikiouzel, und M. Windham. Soft Computing - A Fusion of Foundations, Methodologies and Applications1 (4):
166--179(Dezember 1997)