@book{73682,
	author = {Engeström, Yrjö,},
	title = {Perspectives on activity theory /},
	publisher = {Cambridge University Press,},
	year = {1999},
	series = {Learning in doing},
	address = {New York :},
	note = {Chiefly selected contributions from the Second International Congress for Research on Activity Theory, held in 1990 in Lahti, Finland}
}