| Number | Date | Country | Kind |
|---|---|---|---|
| 3239703 | Oct 1982 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3107090 | Templeton | Oct 1963 | |
| 3175824 | Albosta | Mar 1965 | |
| 4447053 | Wager | May 1984 |
| Number | Date | Country |
|---|---|---|
| 2524359 | Dec 1975 | DEX |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, vol. 16, No. 11, pp. 3676, 3677, Apr. 1974, J. Gutteling. |