Collect. Czech. Chem. Commun.
1975, 40, 1426-1440
https://doi.org/10.1135/cccc19751426
Conformation of ring A of 1,2-disubstituted triterpenes. Geometry and stability of the boat form
J. Klinot, M. Buděšínský, M. Kliment, S. Hilgard and A. Vystrčil