Stefan Bellon Rainer Koschke Giuliano Antoniol Jens Krinke Ettore Merlo 577-591 2007 33 IEEE Trans. Software Eng. 9 http://doi.ieeecomputersociety.org/10.1109/TSE.2007.70725 db/journals/tse/tse33.html#BellonKAKM07