Author
United States. Bureau of Mines
Ashmead, Dever Campbell, 1884-
2
Sisler, James D. 1894-
2
Ashley, Geo. H. 1866-1951
1
Pennsylvania Geological Survey (4th, 1919-)
1
Pennsylvania. Bureau of Topographic and Geologic Survey
1
Pennsylvania. Water and Power Resources Board
1
Reese, John F.
1
United States. Coal Commission
1