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2. N. Parr, British Patent 974 757 (1964).
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4. M. Washburn andH. Baumgartner,ibidin “, p. 479.
5. A. Mclean, E. Fisher andR. Bratton, A.M.M.R.C. Interim Report, Contract No. DAAG 46-71-C10162, 1 July–31 December 1972.