@book{790,
	author = {Piaget, Jean,},
	title = {Main trends in psychology.},
	publisher = {Allen and Unwin,},
	year = {1973.},
	series = {Main trends in the social sciences,},
	address = {London,},
	note = {"Originally published as chapter 3 in Main trends of research in the social and human sciences, Part 1, Mouton/Unesco 1970."}
}