1. D.H. Lloyd:Sheet Metal Ind., 1966, vol. 43, p. 434.
2. M.J. Painter and R. Pearce:Sheet Metal Ind., 1976, vol. 53, pp. 12–19.
3. C. Weidemann:Sheet Metal Ind., 1978, vol. 55, pp. 984–89.
4. H. D. Nine:Mechanics of Sheet Metal Forming, Material Behavior and Analysis, D.P. Koistinen and N-M Wang, eds., Plenum, New York, NY, 1978, pp. 179–211.
5. GM do Brasil:Res. Discl., vol. 147, no. 181, pp. 212–13.