| Number | Date | Country | Kind |
|---|---|---|---|
| 2850271 | Nov 1978 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3575880 | Wojahn et al. | Apr 1971 | |
| 3794299 | Wagner et al. | Feb 1974 | |
| 4017413 | Bittner et al. | Apr 1977 | |
| 4252780 | Koppl et al. | Feb 1981 |
| Number | Date | Country |
|---|---|---|
| 1670731 | Dec 1970 | DEX |
| 2454910 | Dec 1976 | DEX |
| Entry |
|---|
| Ullman, Enzyklopadie Der Technishen Chemie, 3rd Edition, 1951, vol. 1, pp. 743-744 and 769-770. |