Ranking top 25 players in NFL history: Dick Butkus has prominent place on league's all-time list

NFL Heroes: The 100 Greatest Players of All Time: 9780228103479: Johnson, George, Maki, Allan: Books

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Dick Butkus: Most Up-to-Date Encyclopedia, News & Reviews

Ranking top 25 players in NFL history: Dick Butkus has prominent place on league's all-time list

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Who's Better, Who's Best in Football?: Setting the Record Straight on the Top 65 NFL Players of the Past 65 Years: 9781613217269

Who's Better, Who's Best in Football?: Setting the Record Straight on the Top 65 NFL Players of the Past 65 Years

Gale Sayers, the Chicago Bears' Hall of Fame running back, dies at 77: 'He was poetry in motion. His like will never be seen again.' – Hartford Courant

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Dick Butkus, Hall of Fame linebacker and Bears legend, dies at age of 80

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Tommy Nobis, the Atlanta Falcons' first star and best known as 'Mr. Falcon,' passes away