| Number | Date | Country | Kind |
|---|---|---|---|
| 3702968 | Feb 1987 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3689424 | Berg | Sep 1972 | |
| 3966629 | Dumbrell | Jun 1976 |
| Number | Date | Country |
|---|---|---|
| 0026529 | May 1984 | EPX |
| 1922046 | Apr 1977 | DEX |
| Entry |
|---|
| H. Schott, Journal of American Chemical Society, vol. 45, 1968, p. 414. |