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.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Mining Symposium Duluth, Minn, Duluth Branch University of Minnesota, American Institute of Mining and Metallurgical Engineers. Minnesota Section, Eugene P. Pfleider, و 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.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)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.