NFL's Depression-era ban on black players lingers on in the owner's box - Chicago Sun-Times
Throwback: The truth about George Halas and the NFL's ban on black players - Windy City Gridiron
NFL's Depression-era ban on Black players lingers on in the owner's box - The Philadelphia Sunday Sun
Football and the NFL During World War II
ESPN - Haven't been worn since 1936. The Bears are
Super Bowl: What NFL isn't commemorating: 12-year ban on black players
Logos and uniforms of the Chicago Bears - Wikipedia
NFL All-Time Team: George Halas
The NFL's Humble Beginnings