Blai Bonet Patrik Haslum Sarah L. Hickmott Sylvie Thiébaux Directed Unfolding of Petri Nets. 172-198 2008 1 T. Petri Nets and Other Models of Concurrency http://dx.doi.org/10.1007/978-3-540-89287-8_11 journals/topnoc/2008-1 db/journals/topnoc/topnoc1.html#BonetHHT08