@book{3238,
	author = {Hernández Sampieri, Roberto. Fernández Collado, Carlos Baptista Lucio, Pilar},
	title = {Metodología de la investigación.},
	publisher = {Mc Graw Hill / Interamericana},
	year = {1998},
	address = {México D.F.},
	edition = {2ª}
}