Hideharu Kojima Yoshiaki Kakuda Juichi Takahashi Tomoyuki Ohta A model for concurrent states and its coverage criteria. 363-368 2009 ISADS http://dx.doi.org/10.1109/ISADS.2009.5207390 conf/isads/2009 db/conf/isads/isads2009.html#KojimaKTO09