Raging Bull on IMDB
https://www.imdb.com/title/tt0081398/?ref_=nv_sr_1
Comprehensive entry for Raging Bull on the Internet Movie Database
Raging Bull on Rotten Tomatoes
https://www.rottentomatoes.com/m/raging_bull/
Overview of critical reception of Raging Bull on Rotten Tomatoes
About Martin Scorsese
https://www.biography.com/people/martin-scorsese-9476727
Martin Scorsese biography on biography.com