@book{28096,
	author = {Campbell, Donald T. and Stanley, Julian C.},
	title = {Diseños experimentales y cuasiexperimentales en la investigación social.},
	publisher = {Amorrortu,},
	year = {1973.},
	address = {Buenos Aires :},
	edition = {1a ed.},
	note = {Serie Biblioteca de Sociología.}
}