1. 1) T. SUZUKI and T. NAGANo: Joint Meeting MMIJ-AIME, Tokyo, May, 1972
2. 2) T. SUZUKI: The Latin Ameriean Congress on Mining and Extractive Metallurgy, Santiago, Chile, August, 1973
3. 3) T.NAGANO and T. SUZUKI: The 105 th AIME Annual Meeting, Las Vegas, Nevada, February, 1976
4. 5) T. NAGANO and T. SUZUKI: The 15th Annual Conference of the Canadian Institute of Mining and Metallurgy, Ottawa, Canada, August, 1976
5. 6) H.H. KELLOG: The Latin American Congress on Mining and Extractive Metallurgy, Santiago, Chile, August, 1973