1. Pflibsen KP, Milbocker MT. Eye Fundus tracker/stabilizer. US Patent 4856891. 1987
2. Knapp RB, Hake LE, Lusted HS. Method and apparatus for eye tracking for convergence and strabismus measurement. US Patent 5293187. 1992
3. Gerhardt LA, Sabolcik RM. Eye tracking apparatus and method employing Grayscale threshold value. US Patent 5481622. 1994
4. Interrupted reflection fiber optic communication device for the severely disabled;Grattan;J Biomed Eng,1984
5. Communication by eye closure: a microcomputer-based system for the disabled;Grattan;IEEE Trans Biomed Eng BME,1986