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.
A. Aschenbrenner, M. Kuster, C. Ludwig, and T. Vitt. Digital Ecosystems and Technologies, 2009. DEST '09. 3rd IEEE International Conference on, page 745 -750. (June 2009)
L. Page, S. Brin, R. Motwani, and T. Winograd. Proceedings of the 7th International World Wide Web Conference, page 161--172. Brisbane, Australia, (1998)