APA (7th ed.) Citation

Collman, R. D., & Gradle, W. J. (2006). Soil survey of Douglas County, Illinois. Natural Resources Conservation Service.

Chicago Style (17th ed.) Citation

Collman, Ronald D., and William J. Gradle. Soil Survey of Douglas County, Illinois. [Washington, D.C.?]: Natural Resources Conservation Service, 2006.

MLA (9th ed.) Citation

Collman, Ronald D., and William J. Gradle. Soil Survey of Douglas County, Illinois. Natural Resources Conservation Service, 2006.