@book{38253,
	author = {Langford, Peter. and Hovath, Silvia,},
	title = {El desarrollo del pensamiento conceptual en la escuela secundaria /},
	publisher = {Ediciones Paidos,},
	year = {1990.},
	series = {Temas de educaci�on ;},
	address = {Barcelona :},
	note = {Titulo orginal: Concept deveolpement in the secondary school.}
}