1. Andersson, L. & J. Rova. 2004. Rubiaceae-Hippotideae, In: Harling, G. & Andersson, L., Flora of Ecuador 74, 43 pp.
2. Burger, W. & C. M. Taylor. 1993. Fam. 202. Rubiaceae. In: W. Burger (ed.), Flora Costaricensis. Fieldiana, Botany, New Series 33: 212–216.
3. Cornejo X. 2006. Two new species of Pentagonia (Rubiaceae-Hippotideae) from Ecuador and Peru. Harvard Papers in Botany 11(1): 19–24.
4. Cornejo X. 2009. Two new species of Pentagonia (Rubiaceae, Hippotideae) from Colombia and Ecuador. Novon 19: 25–31.
5. Foster, R. B., A. H. Gentry & C. Josse. 1992. Plant List: Cerro Mutiles. Pp. 133–137. In: T. A. Parker III & J. L. Carr (eds.), Status of Forest Remnants in the Cordillera de la Costa and Adjacent Areas of Southwestern Ecuador. Washington, DC: Conservation International, RAP Working Papers 2.