When Jean-Louis Trintignant's character is being grilled, the policeman mentions that witnesses saw a man and a woman. Trintignant responds by whistling a bit of the theme from his previous movie with Claude Lelouche, the international sensation Un homme et une femme (1966).
Jean-Louis Trintignant's character is named Simon Duroc. In the actor's previous movie with this director, the celebrated Un homme et une femme (1966), his character was named Jean-Louis Duroc.
Towards the end of the sequence, early in the film, where Simon is trying on various disguises in the photo booth, there's a single frame closeup of Trintignant making a silly face.
Italian censorship visa # 57551 delivered on 14 January 1971.