R. Hubbard, A. Kropf, THE ACTION OF LIGHT ON RHODOPSIN., in Proc Natl Acad Sci U S A, vol. 44, n. 2, Feb 1958, pp. 130-9, PMID 16590155.
B. Honig, T. Ebrey; RH. Callender; U. Dinur; M. Ottolenghi, Photoisomerization, energy storage, and charge separation: a model for light energy transduction in visual pigments and bacteriorhodopsin., in Proc Natl Acad Sci U S A, vol. 76, n. 6, Jun 1979, pp. 2503-7, PMID 288039.