1. Davidson, J. F., and B. O. G. Schüler. Trans. Inst. Chem. Eng. 38:144 (1960).
2. Maier, C. G. U.S. Bur. Mines Bull. 260 (1927).
3. Okun, D., and J. K. Baars. Proc. Intern. Congr. Surface Active Subst. 4th Congress, Bruxelles (1964) 2:57 (1967).
4. Kovalski, W. von, and A. Wacker. Ber. 63:1698 (1930).
5. Guyer, A., and E. Peterhans. Helv. Chim. Acta 26:1099 (1943).