List of Last Undefeated NFL Teams by Year
Eagles Remain the N.F.L.'s Only Undefeated Team - The New York Times
Cincinnati football before the Bengals
History of the NFL: From the 1890s to the Present - TheStreet
A look at the NFL in the fabulous 1950s
When the College Football Stars Played NFL Champs
Top 15 best NFL rivalries in league history: all-time ranking
NFL's 100 best teams of all time: Who's greatest squad in history?
How Many NFL Teams Have Gone Undefeated in a Season?
Ranking How “All In” Every NFL Team Is for 2023 - The Ringer