1. Airy Shaw, H.K. 1973. A dictionary of the flowering plants and ferns, 8th edn. Cambridge: Cambridge University Press.
2. APG 1998. See general references.
3. APG II 2003. See general references.
4. Baillon, H. 1871. Saxifragacées. Hist. Pl. 3:325–464. Paris: Hachette.
5. Baldwin, J.T. Jr., Speese, B.M. 1951. Penthorum: its chromosomes. Rhodora 53:89–91.