@book{Engestroem:1987,
        title = {Learning by expanding: An activity-theoretical approach to developmental research},
        address = {Helsinki},
        author = {Yrjö Engeström},
        publisher = {Orienta-Konsulit},
        year = 1987,
        biburl = {http://www.bibsonomy.org/bibtex/20a4fa77c8c14efeb2e7c858120ec717d/jeahex},
	keywords = {activity-theory},
    }