| Number | Date | Country | Kind |
|---|---|---|---|
| 2909231 | Sep 1979 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3397767 | Hobbs | Aug 1968 | |
| 3904017 | Frechette | Sep 1975 | |
| 3964595 | Edstrom | Jun 1976 |
| Number | Date | Country |
|---|---|---|
| 2820266 | Nov 1978 | DEX |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, vol. 22, No. 6, Nov. 1979, Schaefer, "Two-Color Cartridge Ribbon System with Correction," pp. 2327-2329. |