Interactive Videoconferencing for collaborative learning at a distance in the school of 21st century: A case study in elementary schools in Greece. - Panagiotes S. Anastasiades; George Filippousis; Labros Karvunis; Spiros Siakas; Arsitokritos Tomazinakis; Panagiota Giza; Hellen Mastoraki (Comput. Educ., 2010)