Darnell J. Moore Roy Want Beverly L. Harrison Anuj Gujar Kenneth P. Fishkin Implementing Phicons: Combining Computer Vision with InfraRed Technology for Interactive Physical Icons. 67-68 1999 ACM Symposium on User Interface Software and Technology http://doi.acm.org/10.1145/320719.322585 db/conf/uist/uist1999.html#MooreWHGF99