by D. A. O'Keefe, Donald E. Kirby, Fun-Den Wang, J. E. Dooley, John M. Gomes, Karl C. Dean, L. C. Headley, Lester J. Crow, Noel N. Moebs, Richard A. Dick, Robert Lynn Crosby, Tedford C. Briggs, United States. Bureau of Mines. Staff, Coal Sampling and Inspection, Victor R. Spironello, C. I. Pierce, Donald H. Desy, Dwight E. Couch, Eben L. Singleton, H. Austin Tucker, Joseph W. Sterner, Kenji Uchida, Meng-Cherng Sun, Robert C. Bates, Ronald F. Kendall, Donald E. Hirsch, Morton Min Wong, Robert M. Doerr, Thomas A. Sullivan, W. K. Sawyer, William C. Hill

1969