by Benton L. Tibbetts, D. G. Kesterke, D. G. Kuehn, Donald W. Mitchell, H. E. Thomas, Harold L. Rhodes, J. M. Kuchta, James H. Russell, James H. Scott, L. C. Headley, Larman J. Heath, Michael John Ferrante, Stephen Krickovic, Thomas E. Green, United States. Bureau of Mines. Staff, Coal Sampling and Inspection, Verne E. Hooker, A. F. Smith, Aldo L. Furno, C. I. Pierce, Charles Findlay, H. C. Carpenter, Jack I. Paige, L. M. Chanin, Lowell Stroud, Ray A. Jones, Wilbur I. Duvall, Danton L. Paulson, Philip C. Tully, Richard G. Burdick, T. E. Sterner, William Edward Wallace

1971