1. K. Ichinose, and T. Masuda:Journal of Japan Institute of Light Metals, Vol. 29, No. II, (1979) 483-490.
2. K. Manabe, and W. Nishimura:Journal of' Japan Society for Technology of' Plasticity, Vol. 24, No. 264, (1983) 47-52.
3. K. Manabe, and H. Nishimura:Journal of' Japan Society for Technology of' Plasticity, Vol. 24, No. 266, (1983) 276-282.
4. A. S. Chumadin and V. I. Ershov:Soviet Forging and Sheet Metal Stamping Technology, No. 2, (1987) 76-79.
5. K. Kitazawa:Journal of Engineering for Industry, Vol. 115, No. 4, (1993) 466-471.