@book {RP-83-02,
	title = {Programmable logic controllers and Petri nets: A comparative study},
	year = {1983},
	pages = {83-88},
	publisher = {Pergamon Press},
	organization = {Pergamon Press},
	author = {M. Silva and S. Velilla},
	editor = {E.A. Puente and G. Ferrate}
}

