1. Flory, P. G. (du Pont de Nemours, E. I., and Co.) US Pat. 2172374 (12 Sept. 1939)
2. New Polyoxamidation Catalysts
3. Thermally induced solid state polycondensation of nylon 66, nylon 6-10 and polyethylene terephthalate
4. Beaton, D. H. (du Pont de Nemours, E. I., and Co.) Ger. Offen. 2 232 304 (18 Jan. 1973)
5. Endo, T., Ihata, J. and Fujimoto, A. (Asahi Chemical Industry Co., Ltd.), Japan. Pat. 73 23 199 (11 July 1973)