| Number | Name | Date | Kind |
|---|---|---|---|
| 3796890 | Thompson et al. | Mar 1974 | |
| 4163161 | Walker | Jul 1979 | |
| 4253055 | Gatten | Feb 1981 | |
| 4300061 | Mihalich et al. | Nov 1981 | |
| 4327320 | Ogvey et al. | Apr 1982 | |
| 4342926 | Whatley | Aug 1982 | |
| 4359680 | Hellums et al. | Nov 1982 | |
| 4442398 | Bertails et al. | Apr 1984 | |
| 4464588 | Wieser | Aug 1984 |
| Number | Date | Country |
|---|---|---|
| 2031193A | Apr 1980 | GBX |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, vol. 22, No. 2, pp. 790 and 791. |