Final Report Ordered by Legislature, 1891: pt. I. Carboniferous formations, by J.P. Lesley, E.V. d'Invilliers, and A. DW. [!] Smith. pt. II. Bituminous coal fields, by E.V. d'Inilliers, and New Red of Bucks and Montgomery counties by B.S. Lymann
Pennsylvania. Geological survey