| Number | Date | Country | Kind | 
|---|---|---|---|
| 2716934 | Apr 1977 | DEX | 
| Number | Name | Date | Kind | 
|---|---|---|---|
| 3706525 | Blackwell et al. | Dec 1972 | |
| 3711245 | Neumer | Jan 1973 | |
| 4049377 | Schwab et al. | Sep 1977 | 
| Entry | 
|---|
| Venkataraman, K., "The Chemistry of Synthetic Dyes", vol. VIII (Academic Press), 1978, pp. 179-180. |