M. Wu, и R. Balakrishnan. UIST '03: Proceedings of the 16th annual ACM symposium on User interface software and technology, стр. 193--202. New York, NY, USA, ACM, (2003)
P. Dietz, и D. Leigh. UIST '01: Proceedings of the 14th annual ACM symposium on User interface software and technology, стр. 219--226. New York, NY, USA, ACM, (2001)