I was at the YES concert on December 5, 1977 in Paris, France. The show was great, of course!
I don't know if you're interested, but the opening act that night was Donovan, who I caught on tour last year - amazingly, his voice still sounds exactly the same.
It was at the Grande Halle at the Porte de Pantin (I still have a ticket stub somewhere) This was a former slaughterhouse which was used frequently for indoor concerts at that time. (David Bowie played there about a week afterwards, also for two nights and I went to a Grateful Dead concert there on October 16, 1982, Bob Weir's 36th birthday)