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2. Beranek, L. L., Acoustics, p. 82 (New York: McGraw-Hill, 1954); SI. 1976/1674.
3. Industrial liquid lubricants (British Standard 4231: 1982). I.S.O. 3448: 1975.
4. Petroleum products and lubricants, p. 269 (Amer. Soc. for Testing Materials, 1956).
5. Bright, C, and Clark, L., Rep. Brit. Ass., 1861, p. 37.