Mining Symposium Duluth, Minn, University of Minnesota, Duluth Branch, American Institute of Mining and Metallurgical Engineers. Minnesota Section, Pfleider, E. P., & Berger, F. E. (1969). Thirtieth annual mining symposium and the Forty-second annual meeting of the Minnesota Section, AIME, January 13-15, 1969, Duluth, Minnesota. University of Minnesota.
Chicago-referens (17:e uppl.)Mining Symposium Duluth, Minn, Duluth Branch University of Minnesota, American Institute of Mining and Metallurgical Engineers. Minnesota Section, Eugene P. Pfleider, och Frederick E. Berger. Thirtieth Annual Mining Symposium and the Forty-second Annual Meeting of the Minnesota Section, AIME, January 13-15, 1969, Duluth, Minnesota. Minneapolis: University of Minnesota, 1969.
MLA-referens (8:e uppl.)Mining Symposium Duluth, Minn, et al. Thirtieth Annual Mining Symposium and the Forty-second Annual Meeting of the Minnesota Section, AIME, January 13-15, 1969, Duluth, Minnesota. University of Minnesota, 1969.