Takashi Hattori Hiroshi Kawakami Osamu Katai Takayuki Shiose Encoding Modalities into Extended Petri Net for Analyzing Discrete Event Business Process. 255-264 2008 New Directions in Intelligent Interactive Multimedia http://dx.doi.org/10.1007/978-3-540-68127-4_27 series/sci/2008-142 db/series/sci/sci142.html#HattoriKKS08