References to Groundhog Day...

It just occurred to me that they named Rita after the character in the movie and the protagonist is also William (or Bill) after Bill Murray.

From IMDb trivia: In the book, Cage awakes at 06:00 hours, like Bill Murray in Groundhog Day (1993), who's also trapped in a never ending day; also Cage in the book says "same old, same old", and Murray got that line too.

What else?