1. Ortega, A. et al, Rev. Latinoam. Quim., 1980, 11, 45
2. Lehmann, L. et al, Phytochemistry, 1988, 27, 2994.
3. Narasimhachari, N. et al, Can. J. Chem., 1961, 39, 2572
4. Arya, V.P. et al, Tetrahedron, 1961, 16, 255
5. Carman, R.M. et al, Aust. J. Chem., 1964, 17, 395