APA

Modern coal mining methods. New York, N. Y. : published by Coal Age 330 west 42nd street, 19: .

Chicago

Modern coal mining methods. New York, N. Y. : published by Coal Age 330 west 42nd street, 19: .

Harvard

Modern coal mining methods. New York, N. Y. : published by Coal Age 330 west 42nd street, 19: .

MLA

New York, N. Y. : published by Coal Age 330 west 42nd street, 19: . .