@book {RP-91-18,
	title = {On the Analysis and Synthesis of Free Choice Systems},
	volume = {483},
	year = {1991},
	month = {11},
	pages = {243-286},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	author = {J. Esparza and M. Silva},
	editor = {G. Rozenberg}
}

