J. MacQueen. Proc. of the fifth Berkeley Symposium on Mathematical Statistics and Probability, 1, Seite 281-297. University of California Press, (1967)
M. Maechler, P. Rousseeuw, A. Struyf, und M. Hubert. (2005)Rousseeuw et al provided the S original which has been ported to R by Kurt Hornik and has since been enhanced by Martin Maechler: speed improvements, silhouette() functionality, bug fixes, etc. See the 'Changelog' file (in the package source).