Subash Shankar Sinan Asa Vladimir Sipos Xiaowei Xu Reasoning about real-time statecharts in the presence of semantic variations. 243-252 2005 conf/kbse/2005 ASE http://doi.acm.org/10.1145/1101908.1101945 db/conf/kbse/ase2005.html#ShankarASX05