R. Dunn, J. McCoy, M. Simsek, A. Majumdar, S. H. Chang, U. L. Rajbhandary, H. G. Khorana,
The bacteriorhodopsin gene Proceedings of the National Academy of Sciences of the United States of America. ,vol. 78, pp. 6744- 6748 ,(1981) ,
10.1073/PNAS.78.11.6744