December 2010 - Inside American Football 1
Today in Pro Football History: 05/01/2015 - 06/01/2015
American Football / Useful Notes - TV Tropes
WLAF/ NFLE The Football Autograph Encyclopedia
European Super League collapse: The global soccer debacle explained and analyzed.
NFL History: 100 objects that tell the story of football - Sports Illustrated
Oral history -- 10 years after NFL Europe's demise, alumni such as Kurt Warner remember developmental league fondly - ESPN
Iowa State Players in Professional Football: Part 4B (1990s) - Wide Right & Natty Lite
The patchy but interesting history of San Antonio football. 6 teams with 6 different leagues! : r/xfl
The Leagues Are Long Gone, But The Cards Live On