1. T. Young, Phil. Trans. Roy. Soc. (London) 95, 65 (1805).
2. W. D. Harkins and A. Feldman, J. Amer. Chem. Soc. 44, 2665 (1922).
3. H. W. Fox and W. A. Zisman, J. Colloid Sci. 5, 514 (1950).
4. W. A. Zisman, Advan. Chem. Ser. No. 43, Am. Chem. Soc., Washington, D. C., 1964, p. 1, and references therein.
5. L. A. Girifalco and R. J. Good, J. Phys. Chem 61, 904 (1957).