1. R.A. Day, R.F. Smart, N. Tommis, Assoc. Eng. Tech. Symp., U.K., Paper No. 4, (1970).
2. A. Pacz. US Patent No. 1387900, (Feb. 1920);
3. British Patent No. 158827, (Jan. 1921).
4. L.M. Leandro, F.R. Serafin, 43rd Int. Foundry Cong. (43 CIF-5), Budapest, Hungary, 1976.