Tunnel and Shaft Conference, Minneapolis, American Society of Civil Engineers, Society of Mining Engineers of AIME, University of Minnesota. School of Mineral and Metallurgical Engineering, Minnesota. University. Dept. of Civil Engineering, & Yardley, D. H. (1970). Rapid excavation--problems and progress: Proceedings. Society of Mining Engineers of the American Institute of Mining, Metallurgical, and Petroleum Engineers.

Tunnel and Shaft Conference, Minneapolis, American Society of Civil Engineers, Society of Mining Engineers of AIME, University of Minnesota. School of Mineral and Metallurgical Engineering, Minnesota. University. Dept. of Civil Engineering, and Donald H. Yardley. Rapid Excavation--problems and Progress: Proceedings. New York: Society of Mining Engineers of the American Institute of Mining, Metallurgical, and Petroleum Engineers, 1970.

Tunnel and Shaft Conference, Minneapolis, et al. Rapid Excavation--problems and Progress: Proceedings. Society of Mining Engineers of the American Institute of Mining, Metallurgical, and Petroleum Engineers, 1970.