| Number | Date | Country | Kind |
|---|---|---|---|
| 4205632 | Feb 1992 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3673169 | Weaver et al. | Jun 1972 | |
| 4994563 | Walter et al. | Feb 1991 | |
| 5208325 | Berneth et al. | May 1993 |
| Entry |
|---|
| J. Chem. Soc., Chem. Commun., 1990, pp. 325 and 326. |
| Dyes and Pigments 16, 1991, pp. 183 to 196. |