BioStor
 | La fauna de la Republica Argentina. E L Holmberg (1898) Segundo censo nacional : 477-602 |
 | The Flora of the Edgehill Ridge near Willow Grove and Its Ecology (1900) Proceedings of The Academy of Natural Sciences of Philadelphia 52: 482-490 |
 | A note on Rafinesque's florula Columbica E L Little (1943) Proceedings of The Biological Society of Washington 56: 57-65 |
 | The genera of Gentianaceae in the southeastern United States R E Weaver Jr. and C E Wood (1982) Journal of the Arnold Arboretum 63: 441-487 |