| Number | Name | Date | Kind |
|---|---|---|---|
| 2455963 | Wheeler | Dec 1948 | |
| 3369427 | Brighton et al. | Feb 1968 | |
| 3394611 | Beurrier | Jul 1968 | |
| 3918021 | Nishioka et al. | Nov 1975 | |
| 4489304 | Hayes | Dec 1984 | |
| 4587510 | Kim | May 1986 | |
| 4670743 | Zemke | Jun 1987 |
| Number | Date | Country |
|---|---|---|
| 2308226 | Nov 1976 | FRX |
| 627545 | Nov 1945 | GBX |
| Entry |
|---|
| IBM Technical Bulletin, vol. 23, #8, Jan. 1981, J. E. Fox. |