Kochendoerfer, Gerd G.; Lin, Steven W.; Sakmar, Thomas P.; Mathies, Richard A. (August 1999). "How color visual pigments are tuned". Trends in Biochemical Sciences. 24 (8): 300–305. doi:10.1016/S0968-0004(99)01432-2. PMID10431173.
Kochendoerfer, Gerd G.; Lin, Steven W.; Sakmar, Thomas P.; Mathies, Richard A. (August 1999). "How color visual pigments are tuned". Trends in Biochemical Sciences. 24 (8): 300–305. doi:10.1016/S0968-0004(99)01432-2. PMID10431173.