Luca Bernardinello Lucia Pomello Stefania Rombolà Orthomodular Lattices in Occurrence Nets. 163-182 2009 Petri Nets http://dx.doi.org/10.1007/978-3-642-02424-5_11 conf/apn/2009 db/conf/apn/pn2009.html#BernardinelloPR09