This comes from an article in a Norwegian magazine from December 1973:

Based on the following text from an article in a Norwegian magazine from December 1973: “[The group were in Oslo.] They came from a TV show in Brussels and were to perform in Norway, before returning to Sweden to conclude a long folkpark tour[.]”

Since the Norwegian performance was on 31 August 1973, this would suggest that they did Belgian TV in late August – if the article is accurate.

No further information available.

Thanks to Carl Magnus Palm.