Roberts, P. (1901). The anthracite coal industry: A study of the economic conditions and relations of the co-operative forces in the development of the anthracite coal industry of Pennsylvania. New York : London: The Macmillan Company ; Macmillan & Co., ltd..

Roberts, Peter. The Anthracite Coal Industry: A Study of the Economic Conditions and Relations of the Co-operative Forces in the Development of the Anthracite Coal Industry of Pennsylvania. New York : London: The Macmillan Company ; Macmillan & Co., ltd., 1901.

Roberts, Peter. The Anthracite Coal Industry: A Study of the Economic Conditions and Relations of the Co-operative Forces in the Development of the Anthracite Coal Industry of Pennsylvania. New York : London: The Macmillan Company ; Macmillan & Co., ltd., 1901.