C. Peters, and M. Zaki. Working Paper Series of the Cambridge Service Alliance, Cambridge, UK, Cambridge Service Alliance, University of Cambridge, (2018)
L. Grunske, and P. Zhang. Proceedings of the the 7th joint meeting of the European software engineering conference and the ACM SIGSOFT symposium on The foundations of software engineering, page 183--192. New York, NY, USA, ACM, (2009)