| Number | Name | Date | Kind |
|---|---|---|---|
| 3839278 | Dexter et al. | Oct 1974 | |
| 4032562 | Dexter et al. | Jun 1977 | |
| 4093587 | Spinack | Jun 1978 | |
| 4132702 | Schmidt et al. | Jan 1979 | |
| 5478875 | Dubs et al. | Dec 1995 | |
| 5663128 | Evans et al. | Sep 1997 |
| Number | Date | Country |
|---|---|---|
| 9113134 | Sep 1991 | WOX |
| Entry |
|---|
| Research Disclosure 38420 (Apr. 1996, No. 384). |