Petroleum. Technology, employment, and output per man in petroleum and natural-gas production; by O. E. Kiessling, H. O. Rogers, G. R. Hopkins, N. Yaworski, R. L. Kiessling, J. Brian Eby, Lew Suverkrop, J. S. Ross, R. E. Beithecker, W. B. Berwald, Andrew W. Rowley, M. A. Schellhardt, Richard Sneddon, Boyd Guthrie, Herbert Schimmel, and J. C. Albright.