To cite NbClust in publications use:
Malika Charrad, Nadia Ghazzali, Veronique Boiteau, Azam Niknafs (2014). NbClust: An R Package for Determining the Relevant Number of Clusters in a Data Set. Journal of Statistical Software, 61(6), 1-36. URL http://www.jstatsoft.org/v61/i06/.
Corresponding BibTeX entry:
@Article{, title = {{NbClust}: An {R} Package for Determining the Relevant Number of Clusters in a Data Set}, author = {Malika Charrad and Nadia Ghazzali and V{\'e}ronique Boiteau and Azam Niknafs}, journal = {Journal of Statistical Software}, year = {2014}, volume = {61}, number = {6}, pages = {1--36}, url = {http://www.jstatsoft.org/v61/i06/}, }