Burov, S. V.; Kaurov, O. A.; Martynov, V. F.; Smirnova, M. P. Chemistry of Natural Compounds, 1980 , vol. 16, # 5 p. 518 - 524 Khimiya Prirodnykh Soedinenii, 1980 , vol. 16, # 5 p. 706 - 714