1. Rickett, H. W., Wild Flowers of the United States, Vol. 3: The southwestern states. McGraw-Hill Book Company, New York, 1966.
2. Rickett, H. W., Wild Flowers of the United States, Texas. McGraw-Hill Book Company, New York, 1966.
3. Munz, P. A. and Keck, D. D., A California flora. University of California press, Berkeley, 1973.