Czibula, Istvan Gergely, et al. “Hierarchical Clustering for Identifying Crosscutting Concerns in Object Oriented Software Systems”. INFOCOMP Journal of Computer Science, vol. 8, no. 3, Sept. 2009, pp. 21-28, https://infocomp.dcc.ufla.br/index.php/infocomp/article/view/267.