Hi everyone, this is my first post

In one of my exams, i am planing to focus on leones`s work and therefore i need the books to some of his films.
Also the books, which some of his work is based on, might be interesting.
I am looking for the books to
1. The good the bad and the ugly
2. Once upon a time in the west
3. Once upon a time in america
looking forward to your answers.
regards
Christian