@book{15,
	author = {González, Raúl A. and Höhn, Guillermo.},
	title = {Ciencias Naturales 9 :},
	publisher = {Puerto de Palos,},
	year = {2001.},
	address = {Buenos Aires :},
	edition = {1ª ed.},
	note = {Ciencias Naturales para 9 año.}
}