1. S. Greenberg, R. Bohnet, Group Sketch: A multi-user sketchpad for geographically-distributed small groups.
2. Videowhiteboard: Video shadows to support remote collaboration;Tang,1991
3. Liveboard: A large interactive display supporting group meetings, presentations, and remote collaboration;Elrod,1992
4. Real-time collaborative coding in a web IDE;Goldman,2011
5. RichReview++: Deployment of a collaborative multi-modal annotation system for instructor feedback and peer discussion;Yoon,2016