J. Sutton Wall. Report on the Coal Mines of the Monongahela River Region, from the West-Virginia State Line to Pittsburgh, Including the Mines on the Lower Youghiogheny River, part I, "Description of the mines." Second Geological Survey of Pennsylvania, report of progress K4. Board of Commissioners for the Second Geological Survey, Harrisburg, 1884. Google Books ip0MAAAAYAAJ; Historic Pittsburgh 00agl8298m; Internet Archive bub_gb_qBQgRge4JF0C, reportoncoalmin00wallgoog, reportoncoalmine00wall.