Svetlana Yarosh Tara Matthews Thomas P. Moran Barton A. Smith What Is an Activity? Appropriating an Activity-Centric System. 582-595 2009 INTERACT (2) http://dx.doi.org/10.1007/978-3-642-03658-3_62 conf/interact/2009-2 db/conf/interact/interact2009-2.html#YaroshMMS09