1. G. Sachs:Z. Metallk., 1924, vol. 16, p. 55.
2. M. Cook and E. C. Larke:J. Inst. Metals, 1945, vol. 71, p. 371.
3. B. Avitzur:Metal Forming, Processes and Analysis, p. 78, McGraw-Hill, N.Y., 1968.
4. A. N. Bramley and N. A. Abdul:Proc. 2nd North Amer. Metallworking Research Conf., SME, Wisconsin, May 1974.