@article {,
	title = {On three variants of rewriting P systems },
	journal = {Theoretical Computer Science},
	volume = {301},
	year = {2003},
	pages = {201-215},
	publisher = {Elsevier},
	address = {Amsterdam (The Netherlands)},
	abstract = {We continue here the study of P systems with string objects processed by rewriting rules, by investigating some questions which are classic in formal language theory: leftmost derivation, conditional use of rules (permitting and forbidding conditions), relationships with language families in Chomsky and Lindenmayer hierarchies.

},
	keywords = {chomsky hierarchy, Lindenmayer systems, Membrane computing, regulated rewriting},
	issn = {0304-3975},
	doi = {10.1016/S0304-3975(02)00581-9 },
	url = {http://www.ingentaconnect.com/content/els/03043975/2003/00000301/00000001/art00581},
	author = {Claudio Ferretti and Giancarlo Mauri and Gheorghe Paun and Claudio Zandron}
}
