Oliva, Gustavo Ansaldi, et al. “Evolving the System’s Core: A Case Study on the Identification and Characterization of Key Developers in Apache Ant”. Computing and Informatics, vol. 34, no. 3, Oct. 2015, pp. 678-24, http://147.213.75.17/ojs/index.php/cai/article/view/3225.