| Number | Name | Date | Kind |
|---|---|---|---|
| 3861131 | Le Chatelier | Jan 1975 | A |
| 4011712 | Egbers et al. | Mar 1977 | A |
| Number | Date | Country |
|---|---|---|
| 161421 | Nov 1975 | CZ |
| 3410246 | Sep 1985 | DE |
| 3410246 | Sep 1985 | DE |
| 4205485 | Aug 1993 | DE |
| 1155150 | Jun 1969 | GB |
| Entry |
|---|
| German Patent Office Search Report Dated Mar. 13, 2000. |