References

For Pentodon

Guo, X., R.-J. Wang, M.P. Simmons, P. P.-H. But, and J. Yu. 2013. Phylogeny of the Asian Hedyotis-Oldenlandia complex (Spermacoceae, Rubiaceae): evidence for high levels of polyphyly and the parallel evolution of dilpophragmous capsules. Molecular Phylogenetics and Evolution 67: 110-122. Google Scholar

Rogers, G.K. 1987. The genera of Cinchonoideae (Rubiaceae) in the southeastern United States. J. Arnold Arb. 68: 137-183. Google Scholar

Rogers, G.K. 2005. The genera of Rubiaceae in the southeastern United States, part II. Subfamily Rubioideae, and subfamily Cinchonoideae revisited (Chiococca, Erithalis, and Guettarda). Harvard Papers in Botany 10: 1-45. Google Scholar

Terrell, E.E. 1991. Overview and annotated list of North American species of Hedyotis, Houstonia, Oldenlandia, and related genera. Phytologia 71: 212-243. Google Scholar