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3. F. Montino, L. Balducci, F. Ferrero, N. Pernicone, US Patent No. 5,221,657, 22 June 1993, to MURST, Rome.
4. US Patent No. 4,163,775, 7 August 1979, to BP Co.
5. US Patent No. 4,568,532, 4 February 1986, to Kellogg, M.W. Co.