| Number | Date | Country | Kind |
|---|---|---|---|
| 94 13368 | Nov 1994 | FRX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3825622 | Robeson et al. | Jul 1974 | |
| 3855357 | Harris et al. | Dec 1974 | |
| 3884994 | Critchfield et al. | May 1975 |
| Number | Date | Country |
|---|---|---|
| 3-52952 | Mar 1991 | JPX |
| Entry |
|---|
| Patent Abstracts of Japan, vol. 15, No. 197 (C-833), May, 1991. |