| Number | Name | Date | Kind |
|---|---|---|---|
| 2030027 | Greenwood | Feb 1936 | |
| 2900898 | Buttner | Aug 1959 | |
| 3359894 | Rydman | Dec 1967 | |
| 3525305 | Daniels | Aug 1970 | |
| 3563104 | Schuster | Feb 1971 | |
| 3603251 | Elsworth et al. | Sep 1971 | |
| 3782277 | Neal | Jan 1974 | |
| 4024812 | Jahn | May 1977 | |
| 4068578 | Delligatti | Jan 1978 | |
| 4068582 | Poitras et al. | Jan 1978 |
| Entry |
|---|
| Draper et al., IBM Tech. Discl. Bulletin, vol. 19, No. 11, Apr. 1977, pp. 4393-4395. |