1. R. J. Priestley and D. W. Leyshon, Proceedings of Fertilizer Industry Round Table, (1969) 16–26.
2. Ruth Blumberg, Fertilizer Society Proceedings, 151 (1975).
3. South African Patent Applications No. 74/4842 and 75/0162.
4. British Patent Specification No. 1,086,438, October (1967).
5. Paper No. AI/75/18 presented at joint ANDA/ISMA meeting in Sao Paulo, Brazil, April (1975).