1. Y. Hashimoto, “Thin-layer Chromatography,” Hirokawa Publishing Co., Tokyo, 1975, p. 49.
2. S. Yasuda, K. Satoh, T. Ishii and T. Furuya, “Fermentation Technology Today,” ed. by G. Teruiet al., Society of Fermentation Technology, Japan, 1972, p. 697.