Radu Dondera Chun Jia Voicu Popescu Cristina Nita-Rotaru Melissa Dark Cynthia S. York Virtual Classroom Extension for Effective Distance Education. 64-74 2008 28 IEEE Computer Graphics and Applications 1 http://doi.ieeecomputersociety.org/10.1109/MCG.2008.19 db/journals/cga/cga28.html#DonderaJPNDY08