Memoirs of The New York Botanical Garden
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of Vascular Plants of Northeastern United States and adjacent Canada
Acevedo-Rodríguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.
- Characters of the family. By far the largest genus of the family, with about 800 species, in tropical to temperate areas.