Undefeated seasons by the Bears
Chicago Bears, American Football Database
The day the Bears beat the Saints in the NFC championship - Windy City Gridiron
Chicago Bears - 1951 Season Recap
The Chicago Bears 1940 NFL Title: Revenge of the Crybabies
Bears–Packers rivalry - Wikipedia
RECAP: Chicago Bears defeat Seattle Seahawks in second preseason game
National Football League - 1927 NFL Teams
Chicago Bears - 1923 Season Recap