Claudine Chaouiya Elisabeth Remy Denis Thieffry Qualitative Petri Net Modelling of Genetic Networks. 95-112 2006 journals/tcsb/2006-6 T. Comp. Sys. Biology http://dx.doi.org/10.1007/11880646_5 db/journals/tcsb/tcsb6.html#ChaouiyaRT06