A syllabus of Pennsylvania geology and mineral resources - Ashley, Geo. H. (George Hall), 1866- (Harrisburg : Department of internal affairs, Topographic and geologic survey, 1931)
"Publications of the present [Pennsylvania] Geological survey": p. 147-150.
"Publications of the second Geological survey": p. 152-154.
"List of U. S. Geological survey publications on Pennsylvania": p. 155-158.
Keywords: Geology -- Pennsylvania; Mines and mineral resources -- Pennsylvania; Geology -- Pennsylvania -- Bibliography