Diment, W.H., and Urban, T.C., 1981, Average elevation of the conterminous United States (Gilluly averaging method): U.S. Geological Survey Geophysical Investigations Map GP-0933, 2 sheets, scale 1:2,500,000.
Diment, W.H., and Urban, T.C., 1981, Average elevation of the conterminous United States (Gilluly averaging method): U.S. Geological Survey Geophysical Investigations Map GP-0933, 2 sheets, scale 1:2,500,000.
Geophysical Survey, Tectonic Geomorphology,