@ARTICLE {
	AUTHOR = "Marcelo Arenas and Jorge P{\'e}rez and Juan Reutter and Cristian Riveros",
	TITLE ="The Language of Plain SO-tgds: Composition, Inversion and Structural Properties",
	JOURNAL = "Journal of Computer and System Sciences (JCSS)",
	VOLUME = "79",
	NUMBER = "6",
	PAGES = "763-784",
	MONTH = "Sep",
	YEAR = "2013",
	PUBLISHER = "Elsevier Science",
	ADDRESS = "Amsterdam, The Netherlands",
	ISSN = "0022-0000"
	}