1. A. B. Burg and H. I. Schlesinger, J. Am. Chem. Soc. 55, 4020 (1933).
2. L. J. Edwards and R. K. Pearson, US Patent 3,205,255 (1965).
3. W. Schechter, US Patent No. 681,457 (1957).
4. J. D. Bush, R. A. Carpenter and W. Schechter, US Patent 3,014,059 (1961).
5. J. I. Kroschwitz and M. Howe-Grant, Kirk-Othmer Encyclopedia of Chemical Technology, Volume 4, 4th edn. Wiley, New York, NY (1992).