1. J. Greenstein and M. Wintz, “The Chemistry of Amino Acids,” Vol. 2, John Wiley & Sons, Inc., New York, 1961, pp. 736.
2. H. Okai and N. Ishibashi, Abstracts of Papers 8th Symposium of Peptide Chemistry, Tokyo, 1970, pp. 66.
3. N. Ishibashi, H. Okai and T. Oka, 46th National Meeting of Nippon Nogeikagaku Kai, Tokyo, April, 1971, p. 165.