Prabhu, Puniethaa, and Karuppusamy Duraiswamy. “An Efficient Visual Analysis Method for Cluster Tendency Evaluation, Data Partitioning and Internal Cluster Validation”. COMPUTING AND INFORMATICS, vol. 32, no. 5, Jan. 2014, pp. 1013-37, https://www.cai.sk/ojs/index.php/cai/article/view/1982.