For Thaspium
Cooperrider, T.S. 1985. Thaspium and Zizia in Ohio. Castanea 50: 116-119. Google Scholar
Coulter, J.M., and J.N. Rose. 1900. Monograph of the North American Umbelliferae. Contr. U.S. Nat. Herb. 7: 1-256. Google Scholar
Floden, A.J. 2019. Distribution of Thaspium chapmanii and T. barbinode (Apiaceae) in Missouri. Missouriensis 37: 45-49. Google Scholar
Mathias, M.E., and L. Constance. 1945. Umbelliferae. North American Flora, vol. 28B: 43-397. N.Y. Botanical Garden, New York. Google Scholar
Plunkett, G.M., M.G. Pimenov, J.-P. Reduron, E.V. Kljuykov, B.-E. van Wyck, T.A. Ostroumova, M.J. Henwood, P.M. Tilney, K. Spalik, M.F. Watson, B.-Y. Lee, F.-D. Pu, C.J. Webb, J.M. Hart, A.D. Mitchell, and B. Muckensturm. 2018. Apiaceae. In Kadereit, J., & V. Bittrich. 2018. The families and genera of flowering plants. XV. Flowering plants. Eudicots. Apiales, Gentianales (except Rubiaceae). Springer, Cham. Google Scholar