Touchscreens are available on more and more devices, from phones up to desktop screens. Your app should respond to their touch in intuitive and beautiful ways.
E. Bakke, D. Karger, and R. Miller. Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, page 2541--2550. New York, NY, USA, ACM, (2011)
C. Batini, T. Catarci, M. Costabile, and S. Levialdi. Proceedings of the IFIP TC2/WG 2.6 Second Working Conference on Visual Database Systems II, page 153--168. Amsterdam, The Netherlands, The Netherlands, North-Holland Publishing Co., (1992)