Wenz et al. Justus Liebigs Annalen der Chemie, 1958 , vol. 618, p. 210,215, 219 Tanaka Yakugaku Zasshi, 1956 , vol. 76, p. 1314,1317 Chem.Abstr., 1957 , p. 3607 Viscontini et al. Helvetica Chimica Acta, 1949 , vol. 32, p. 1478,1483 Wakisaka; Ishida Journal of Vitaminology, 1959 , vol. 5, p. 44,49