| Canada (North America) |
| Chile (South America) |
| United States (North America) |
| Ecuador (South America) |
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Marticorena, C. & M. Quezada. 1985. Catálogo de la Flora Vascular de Chile. Gayana, Bot. 42: 1–157.
http://www.tropicos.org/Reference/1592
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Gleason, H. A. 1968. The Sympetalous Dicotyledoneae. vol. 3. 596 pp. In H. A. Gleason Ill. Fl. N. U.S. (ed. 3). New York Botanical Garden, New York.
http://www.tropicos.org/Reference/1707
