Hirotake Yamazoe Akira Utsumi Tomoko Yonezawa Shinji Abe Remote gaze estimation with a single camera based on facial-feature tracking without special calibration actions. 245-250 2008 ETRA http://doi.acm.org/10.1145/1344471.1344527 conf/etra/2008 db/conf/etra/etra2008.html#YamazoeUYA08