Sesquiterpenoid derivatives from Ferula ferulaeoides - Isaka,K.; Nagatsu,A.; Ondognii,P.; Zevgeegiin,O.; Gombosurengyin,P.; Davgiin,K. (Chem Pharm Bull 2001; 49 : 1072 - 6; Erratum: Chem Pharm Bull, 2002)