Primary References:
Arnold, Gene. 1976. Plants of the Northern Hemisphere. New York: MacMillan. 331-336.
Grehan, Farrell. 1964. The Odyssey Book of American Wildflowers. New York: The Odyssey Press. 101.
Grey-Wilson, Christopher. 1993. Poppies. Portland: Timber Press. 46-48, 23-27.
Grimm, William Carey. 1968. Recognizing Flowering Wild Plants. Harrisburg: The Stackpole Company. 111.
House, Homer D. 1934. Wild Flowers. New York: MacMillan. 117.
Hylander, Clarence J. 1954. The MacMillan Wild Flower Book. New York: MacMillan. 137.
Krochmal, Arnold & Connie. 1973. A Guide to the Medicinal Plants of the United States. New York: New York Times Book Co. 200.
Mabey, Richard. 1996. Flora Britannica. London: Chatto and Windus. 50-56.
Sanders, Jack. 1993. Hedgemaids and Fairy Candles: The Lives and Lore of North American Wildflowers. McGraw Hill: Ragged Mountain Press. 100-105.
World Wide Web Resources:
University of California at Berkeley. Specimen Management System for Herbaria. http://www.mip.berkeley.edu/query_forms/browse_smasch_chkl.html