Kupchan, S. Morris; Aynehchi, Y.; Cassady, John M.; McPhail, A. T.; Sim, G. A.; Shnoes, H. K.; Burlingame, A. L. (1966). «The isolation and structural elucidation of 2 novel sesquiterpenoid tumor inhibitors from Elephantopus elatus». Journal of the American Chemical Society88 (15): 3674-3676. doi:10.1021/ja00967a056.