(2)  Zimmer, Brigitte & Greater, Werner ed.  1998.  Taxon-journal of the international
       association for plant taxonomy.  Fuldaer Verlagsanstalt Gmbtt, Falda, Germany.  p. 981.

(3)  Moore, David M. ed.  1988.  The Marshall Cavendish Illustrated Encyclopedia of Plants
       & Earth Sciences V. 2.  Marshall Cavendish Corporation.  Freport, N.Y.  Copywrite
       Equinox (Oxford).  p. 173.

(4)   Weed Science of Oregon State University -Weed Programs in Oregon

(5)   Healthgate - Building a better understanding of Health on the web...

(6)   USDA

(7)    Native Plants of Montara Mountain

(8)    Fire Effects Information Systems -FEIS

(9)    Index Kewensis 2.0 c Oxford University Press 1997.
         Index Kewensis data is the copyright of the Trustees of the Toyal Botanic Gardens, Kew.

(10)  Environmental Affairs Office -of Washington State Department of Transportation
 
(11)   Finnish lepidoptera

(12)   The Marion Ownbey Herbarium -Department of Botany Washington State University

(13)   Digital Library Project of the University of California, Berkeley
 
(14)   Flowering Plant Gateway -Acompiled list of sites for the plant family

(15)   University of Maryland Herbarium -Indices Nominum Supragenericorum Plantarum Project
 
(16)    University of Georgia Herbarium (Botany) - Department of Botany at UGA

(17)   Niering, William A. and Olmstead, Nancy C.  ed.  1979.  The Audubon Society field guide to
          N. American Wild Flowers.  Alfred A. Knopt, Chanticleer Press Ink.  New York. p. 331, 193.