Football: Officials and Refs
Kickoff 2017: A look at football chain gangs
Officials' Responsibilities & Positions
Football Referee and Chain Crew Equipment
Everything you ever wanted to know about the crew that moves the chains in the NFL - ESPN
Why the NFL Still Uses Chains to Measure First Downs
South Gulf Football Officials Association
Trial run in 2014 preseason will assess effectiveness of 8-man crew
Football referee mechanics explained - CougCenter
Why the NFL Still Uses Chains to Measure First Downs
Half of CCSD middle school football season canceled as referee shortage continues
DAMLUX Football Referee Chain Clips,Football Yard Officials Markers,Official Football Referee Gear,Nylon Football Numbered Wrist Down Indicator : Sports & Outdoors