Ekkart Kindler Laure Petrucci Towards a Standard for Modular Petri Nets: A Formalisation. 43-62 2009 Petri Nets http://dx.doi.org/10.1007/978-3-642-02424-5_5 conf/apn/2009 db/conf/apn/pn2009.html#KindlerP09