J. A. Hartigan and P. M. Hartigan (1985) The Dip Test of
Unimodality, Annals of Statistics, 13, 70-84.
Tantrum, J., Murua, A. and Stuetzle, W. (2003) Assessment and
Pruning of Hierarchical Model Based Clustering, Proceedings of the
ninth ACM SIGKDD international conference on Knowledge discovery and
data mining, Washington, D.C., 197-205.