*Thierer, John W., Niering, William A., and Olmstead, Nancy C. (2001) "National Audubon Society Field Guide to North American Wildflowers, Eastern Region", Revised Edition.
* Thierer, John W., Niering, William A., and Olmstead, Nancy C. (2001) "National Audubon Society Field Guide to North American Wildflowers, Eastern Region", Revised Edition.