| Europa League 1973/1974 - Appearances as Referee |  |
 |
 |
||||
| 03/10/1973 | Grazer AK | - | Panachaiki GE | 0:1 | 2 | - | 1 |
| 07/11/1973 | TJ Tatran Prešov | - | VfB Stuttgart | 3:5 aet | 4 | - | 1 |
| Europa League 1973/1974 - Appearances as Referee | |
|
|
||||
| 03/10/1973 | Grazer AK | - | Panachaiki GE | 0:1 | 2 | - | 1 |
| 07/11/1973 | TJ Tatran Prešov | - | VfB Stuttgart | 3:5 aet | 4 | - | 1 |
| Complete name: | Karl Keller |
| Born: | 01/04/1923 |
| Place of birth: |
Switzerland |
| Residence: | Basel |
| Nationality: |
Switzerland |