NFL season begins with questions on pass interference replay - Los Angeles Times
Tech: A closer look at the NFL's instant replay camera work
Hawk-Eye NFL Football Operations
How a Smart Endzone Camera Can Improve Your Football Program
Dec. 7, 1963: Video Instant Replay Comes to TV
Instant replay hi-res stock photography and images - Alamy
Replay review in gridiron football - Wikipedia
States Experiment With Instant Replay in High School Football
History of Instant Replay
Lack of cameras on the goal line limits refs' replay rulings - NBC Sports
PLAY FAST & AGGRESSIVE WITH EDGE FOR SIDELINE INSTANT REPLAY