1. City of trees;Bradley,1987
2. Eastern forests;Kricher,1988
3. Local Climatological Data, Washington, DC National Airport. Annual Summary 1994. National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, North Carolina.
4. Allergy in the world;Roth,1978
5. Allergens and other factors important in atopic disease;Gutman,1980