M. Bu, S. Luo, и J. He. Computer-Aided Industrial Design Conceptual Design, 2009. CAID CD 2009. IEEE 10th International Conference on, стр. 973 -976. (ноября 2009)
J. MacQueen. Proceedings of the 5th Berkeley Symposium on Mathematical Statistics and Probability - Vol. 1, стр. 281--297. University of California Press, Berkeley, CA, USA, (1967)