J. Meskens, J. Vermeulen, K. Luyten, and K. Coninx. Proceedings of the working conference on Advanced visual interfaces, page 233--240. New York, NY, USA, ACM, (2008)
J. Ziegler, M. Graube, A. Suhrbier, N. Wessel, H. Malberg, and L. Urbas. Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services, page 191--200. New York, NY, USA, ACM, (2011)