1. Westöö, G., and Norén, K., Acta Chem. Scand., 24, 1639 (1970).
2. Lloyd-Jones, C. P., Nature, 229, 65 (1971).
3. Frost, K. R., and Ware, G. W., Agricultural Engineering, 51, 460 (1970).
4. Monsanto Company Tech. Bull., No. PL-306, 50 (1960).
5. Encyclopedia of Chemical Technology, 5, 289 (1964).