1. and assignees to Imperial Chemical Company, Ltd., Brit. Pat. # 1,156,217 (June 25, 1969).
2. ?Resinography of Cellular Plastics,? ASTM STP, 414, 3 (1967).
3. ?Foams,? Ch. 2, Springer-Verlag New York, Inc., New York (1973).
4. Rubber Age, pg. 58 (January 1974).
5. and ?The Mechanism of Foam Formation? in ?Plastic Foams,? edited by and p. 39, Marcel Dekker, Inc., New York (1972).