1. Wurtz A (1849) Ann 71: 326
2. Pinner S H (1947) Plastics 11: 257
3. Bayer O, Rinke H, Siefken W, Orthner L, Schild (1942) Ger Pat 728981
4. Bayer 0 (1947) Angew Chem 59: 275
5. SRI International (1987) Chemical Economics Handbook, Diisocyanates and Polyisocyanates