A study of roof in Pennsylvania mines contiguous to Monongahela River / by J.W. Paul and J.G. Calverley.
|Main Author:||Paul, James Washington.|
|Other Authors:||Calverley, J. G.|
Washington, D.C. : U.S. Dept. of the Interior, Bureau of Mines, 1933.
Coal mines and mining
"Third paper on groups of representative mines in Pittsburgh coal bed in Western Pennsylvania."
31 p. :
illus., maps ;
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