References
For Oxypolis
Feist, M.A.E., and S.R. Downie. 2008. A phylogenetic study of Oxypolis and Ptilimnium (Apiaceae) based on nuclear rDNA ITS sequences. Syst. Bot. 33: 447-458. Google Scholar
Feist, M.A.E., S.R. Downie, A.R. Magee, and M. (R.) Liu. 2012. Revised generic delimitations for Oxypolis and Ptilimnium (Apiaceae) based on leaf morphology, comparative fruit anatomy, and phylogenetic analysis of nuclear rDNA ITS and cpDNA trnQ-trnK intergenic spacer sequence data. Taxon 61: 402-418. Google Scholar
Kral, R. 1981a. Notes on some "quill"-leaved umbellifers. Sida 9:124-134. 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
Tucker, A.O., N.H. Dill, T.D. Pizzolato, and R.D. Kral. 1983. Nomenclature, distribution, chromosome numbers, and fruit morphology of Oxypolis canbyi and O. filiformis (Apiaceae). Syst. Bot. 8: 299-304. Google Scholar