| Number | Name | Date | Kind |
|---|---|---|---|
| 3995748 | Looney | Dec 1976 | |
| 4134672 | Burlew et al. | Jan 1979 | |
| 4248525 | Sterrett | Feb 1981 |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, vol. 18, No. 9, Feb. 1976, p. 2807. |
| IBM Technical Disclosure Bulletin, vol.18, No. 10, Mar. 1976, pp. 3160-3161. |