1. P.J. Bernstein, CIPO Pat. No. 2,037,297, February 28, 1991.
2. S.F. Chou, W. Roberson, U.S. Pat. No. 5,019,459, April, 1990.
3. D.P. Lomax, R.M. Boggs, U.S. Pat. No. 4,399,198, July 20, 1981.
4. S.F. Chou, U.S. Pat. No. 5,185,162, June, 1991.
5. Cobalt and cobalt alloys,1992