1. Michigan Trees;Barnes,1981
2. Trees of the Northern United States and Canada;Farrar,1995
3. Airborne and Allergenic Pollen of North America;Lewis,1983
4. A Field Guide to Texas Trees;Simpson,1999
5. Die Erreger des Heufiebers: Medizinischbotanische Dokumentation der Pollenallergie in Mitteleuropa;Horak,1979