North C, Dwyer T, Lee B, Fisher D, Isenberg P, Robertson G, Inkpen K. Understanding Multi-touch Manipulation for Surface Computing. In: INTERACT '09: Proceedings of the 12th IFIP TC 13 International Conference on Human-Computer Interaction. INTERACT '09: Proceedings of the 12th IFIP TC 13 International Conference on Human-Computer Interaction. Berlin, Heidelberg; 2009. p. 236?249.