1. S.P. Keeler: Sheet Met. Ind., 1965, vol. 42, pp. 683–91.
2. G.M. Goodwin: Technical Paper No. 680093, SAE, Warrendale, PA, 1968, pp. 380–87.
3. W.B. Hutchinson, R. Arthey, and P. Malmstrom: Scripta Metall., 1976, vol. 10, pp. 673–75.
4. A.J. Renta-Escola: Met. Technol., 1980, vol. 7, pp. 45–49.
5. H. Herø, S. Ekelund, and A.S. Korhonen: Scand. J. Metall., 1979, vol. 8, pp. 254–60.