Mark Ackerman Marleen Huysman John M. Carroll Barry Wellman Giorgio De Michelis Volker Wulf Communities and technologies: an approach to foster social capital? 406-408 2004 conf/cscw/2004 CSCW http://doi.acm.org/10.1145/1031607.1031675 db/conf/cscw/cscw2004.html#AckermanHCWMW04