1. Held R. Clawson M. U.S. Soil Erosion Rates--Myth and Reality (John Hopkins Univ. Press Baltimore 1965).
2. Trimble S., Lund S., J. Soil Water Conserv37, 355 (1982);
3. Batie S., Soil Erosion: Crisis in America's Croplands (The Conservation Foundation, Washington, DC, 1983);
4. Trimble S. Agric. Hist 59 162 (1985).
5. Crosson P. [letter] Science 1995);