I marked it with a footnote containing the writer's name, the work's title and copied the "Publisher" section from Wikipedia so far.
What about the English translation of the original French quote?
I read this one among the answers here on writing.stackexchange:
- Copyright is for a finite amount of time, basically life of the author plus 70 years, or if the copyright is owned by an organization rather than a person, or if the author is anonymous, for 95 years from date of publication.
- A translation has a separate copyright from the original work, with the clock starting from when the translation was published, not the original work.
- Under the "fair use doctrine", you can quote short excerpts from copyrighted works without getting permission.
If this is right (official source would be much appreciated) then I clearly can quote the line in both languages. The translation is also old enough.
So the question is maybe more like if I need to place the footnote? The character will tell his partner the writer's name also the title of the writing later on.