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2. Ardis, A. E. (to B.F. Goodrich Co.), U.S. Patent 2.467.927 (1949).
3. Coover, H. W., Jr., and Shearer, N. H., Jr. (to Eastman Kodak Co.), U.S. Patent 2,794,788 (1957).
4. Coover, H. W., Jr., and Shearer, N. H., Jr. (to Eastman Kodak Co.), U.S. Patent 2,763,585 (1956).
5. Coover, H. W., Jr., and Shearer, N. H., Jr. (to Eastman Kodak Co.), U.S. Patent 3,221,745 (1965).