1. Dorough, G.L., U.S. Patent 2,524,432, October 3, 1950.
2. Durbetaki, A.J., Anal. Chem.,28, 2000 (1956).
3. Erickson, J.G., U.S. Patent 2,567,842, September 11, 1951.
4. Henkel and Cie. British Patent 735,001, August 10, 1955.
5. Kester, E.B., Gaiser, C.J., and Lazar, M.E., J. Org. Chem.,8, 550 (1943).