NbClust package for determining the best number of clusters
Malika Charrad <malika.charrad.1@ulaval.ca> and
           Nadia Ghazzali <nadia.ghazzali@uqtr.ca> and
           Veronique Boiteau <veronique.boiteau.1@ulaval.ca> and
	   Azam Niknafs <azam.niknafs.1@ulaval.ca>
NbClust package provides 30 indices for determining the optimal number of clusters in a dataset.