Inhibition of the tumor-promoting action of 12-O-tetradecanoylphorbol-13-acetate by some oleanane-type triterpenoid compounds. - Nishino,H.; Nishino,A.; Takayasu,J.; Hasegawa,T.; Iwashima,A.; Hirabayashi,K.; Iwata,S.; Shibata,S. (Cancer Res, 1988)