Bioactive oleanolic acid saponins and other constituents from the roots of Viguiera decurrens - Marquina,S.; Maldonado,N.; Garduño-Ramírez,M.L.; Aranda,E.; Villarreal,M.L.; Navarro,N.; Bye,R.; Delgado,G.; Alvarez,L. (Phytochemistry, 2001)