1. A. Stoll and W. Kreis, Helv. Chim. Acta, 16, 1049, 1390 (1933).
2. V.S. Kartashov, Farmatsiya (Moscow), 41, 26 (1992).
3. V.S. Kartashov, S.V. Shorshnev and A.P. Azamastev, Khim. Farm. Zh., 26, 124 (1992).
4. B.T. Brown and S.E. Wright, J. Am. Pharm. Assoc., 49, 777 (1960).