Questionable USFL First Down Sparks Debate Over Microchip Use In NFL
NFL's first-down chains malfunctioned twice on road to Super Bowl. Is there a better way? - The Athletic
Why the NFL Still Uses Chains to Measure First Downs
Super Bowl LIV: How NFL Measures First Downs Is Primitively Low-Tech
Pi**ed is an understatement - USFL players unhappy about chip technology used in footballs
Questionable USFL First Down Sparks Debate Over Microchip Use In NFL
USFL introduces technology to automate official first down decisions - Sports Illustrated
Break the Chain: The USFL's Virtual 1st Down Measurements Are Working
We Must Protect Football's Chain Gang at All Costs - The Ringer
First-down spots limit the necessity for too many measurements – Football Zebras
USFL Using Football Chips To Measure 1st Downs
Sensors in Ball Argument : r/nfl