@inproceedings{streit09,
	author = {Marc Streit and Hans-J\"org Schulz and Dieter Schmalstieg and Heidrun Schumann},
	title = {Towards Multi-User Multi-Level Interaction},
	booktitle = {CoVIS'09: Proceedings of the Workshop on Collaborative Visualization on Interactive Surfaces},
	year = {2009}
}