Lerina Aversano Luigi Cerulo Massimiliano Di Penta How Clones are Maintained: An Empirical Study. 81-90 2007 conf/csmr/2007 CSMR http://doi.ieeecomputersociety.org/10.1109/CSMR.2007.26 db/conf/csmr/csmr2007.html#AversanoCP07