University of Minnesota

University of Toronto, Botany Department

The American Academy of Allergy, Asthma and Immunology and The National Allergy Bureau

Steyermark, Julian A (1975), Flora of Missouri, 4th ed., Ames, Iowa: The Iowa State University Press.

Jelks MD, Mary, Allergy Plants, Tampa, Florida: World Wide Publications.

Smith, E Grant (1990), Sampling and Identifying Allergenic Pollens and Molds, San Antonio, Texas: Blewstone Press.

The Pollen Monitor, Newsletter of Multidata, Inc., Volumes 1-5, 1995-1998.