When did the NFL add the modified, “kicking ball” & are the footballs used for kickoffs the same as those used for FG's? Was it before or after they moved the goalposts
What happens if an NFL kicker entirely misses the ball on a kickoff? - Quora
Ball spots itself at the 20 for the touchback, after a kickoff into the end zone : r/nevertellmetheodds
Field Goal! The Science Behind a Perfect Football Kick
Why does an NFL kicker only take two steps before kicking and not more? - Quora
Evolution of the NFL Rules
Evolution of the NFL Rules
What does the NFL do with game balls after the game? - Quora
NFL Rulebook NFL Football Operations
When did passing overtake running the ball in importance in the NFL? - Quora