1. D. James, Materials Science and Engineering,4, No. 1 (1969).
2. J. Jensen, Light Metal Age, 22, snNo. 11 (1964).
3. G. Weissman and W. Babington, J. of Environmental Sciences,2, No. 5 (1966).
4. G. S. Pisarenko et al., Vestnik Mashinostroeniya, No. 10 (1969).
5. Yu. K. Favstov, Zavod. Lab.,25, No. 5 (1959).