Genotoxic and anti-genotoxic properties of Calendula officinalis extracts in rat liver cell cultures treated with diethylnitrosamine - Perez-Carreon,J.I.; Cruz-Jimenez,G.; Licea-Vega,J.A.; Arce Popoca,E.; Fattel Fazenda,S.; Villa-Trevino,S. (Toxicol In Vitro, 2002)