SAMUEL THOMAS (September 1899). "REMINISCENCES OF THE EARLY ANTHRACITE-IRON INDUSTRY". TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS (reprint by TheHopkinThomasProject.com). Diarsipkan dari versi asli tanggal 14 March 2014. Diakses tanggal 5 December 2016.
SAMUEL THOMAS (September 1899). "REMINISCENCES OF THE EARLY ANTHRACITE-IRON INDUSTRY". TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS (reprint by TheHopkinThomasProject.com). Diarsipkan dari versi asli tanggal 14 March 2014. Diakses tanggal 5 December 2016.