| Europa League 1967/1968 - Appearances as Referee |  |
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| 19/09/1967 | Malmö FF | - | Liverpool FC | 0:2 | - | - | - |
| 15/05/1968 | Leeds United | - | Dundee FC | 1:0 | - | - | - |
| Europa League 1967/1968 - Appearances as Referee | |
|
|
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| 19/09/1967 | Malmö FF | - | Liverpool FC | 0:2 | - | - | - |
| 15/05/1968 | Leeds United | - | Dundee FC | 1:0 | - | - | - |
| Complete name: | Wilhelmus Jacobus Maria Schalks |
| Born: | 21/03/1923 † 25/10/2017 |
| Place of birth: |
Leiden, 
Netherlands |
| Residence: | Leiden |
| Nationality: |
Netherlands |