Gershenzon, J., Pfeil, R. M., Liu, Y. L., Mabry, T. J., & Turner, B. L. (1984). Sesquiterpene lactones from two newly-described species of Vernonia: V. jonesii and V. pooleae. Phytochemistry, 23(4), 777-780. doi:10.1016/S0031-9422(00)85024-4.