1. J. R. Ruhoff, in “Organic Synthesis,” Vol. 2, ed. by A. H. Blatt, Wiley, New York, 1943, pp. 292–294.
2. W. W. Hartmann, J. R. Byers, and J. B. Dickey, in “Organic Synthesis,” Vol. 2, ed. by A. H. Blatt, Wiley, New York, 1943, pp. 322–323.
3. D. D. Whyte, U. S. Patent 3,579,548 (May 18, 1971).
4. Y. Fujino, “Shishitsu Bunsekihou Nyumon,” ed. by I. Uritani, K. Shimura, D. Nakamura, and M. Funazu, Gakkai Shuppan Center, Tokyo, 1978 (in Japanese).
5. AOCS Official Method Cc 3-25, 2nd Ed., Vol. 2, AOCS, Chicago, 1964.