Author
Fergusson, William B., 1924-
1 results
Geological Survey (U.S.)
1 results
Hickok, W. O. (William Orville), 1905-
1 results
Moyer, Forrest Theodore, 1906-
1 results
Pennsylvania. Bureau of Topographic and Geologic Survey
1 results
Pennsylvania. Department of Internal Affairs
1 results
Prather, Bruce A.
1 results
Schweinfurth, Stanley P.
1 results
Shaulis, James R.
1 results
Steidl, Peter F.
1 results
United States. Bureau of Mines
1 results