Béatrice S. Hasler Thierry Buecheler Rolf Pfeifer Collaborative Work in 3D Virtual Environments: A Research Agenda and Operational Framework. 23-32 2009 HCI (12) http://dx.doi.org/10.1007/978-3-642-02774-1_3 conf/hci/2009-12 db/conf/hci/hci2009-12.html#HaslerBP09