found: Its Official rules and statistics, 1935-
found: Football for all..., 2004:p. 36 (NFL absorbed the American Football League (1926-1927) on Aug. 17, 1927)
found: LAC internal file, August 28, 2019(access point: National Football League; variant: NFL)
found: Wikipedia, viewed Sept. 11, 2023(The National Football League (NFL) is a professional American football league that consists of 32 teams, divided equally between the American Football Conference (AFC) and the National Football Conference. The NFL was formed in 1920 as the American Professional Football Association before renaming itself the National Football League for the 1922 season. A new professional league, the fourth American Football League, began to play in 1960. The two leagues announced a merger on June 8, 1966, to take full effect in 1970.) - https://en.wikipedia.org/wiki/National_Football_League
