You can't be the player's friend': inside the secret world of tennis umpires | Tennis | The Guardian
Who was the line judge hit by a tennis ball struck by Novak Djokovic at the US Open? | The US Sun
The hardest part about being a tennis line umpire
About a linesman - TENNIS
In defaulting Djokovic, US Open referee Soeren Friemel deserves credit
Tennis referee hi-res stock photography and images - Alamy
The U.S Open replaces human line judges with optical technology : NPR
Official (tennis) - Wikipedia
A working life: The tennis umpire | Work & careers | The Guardian
Officiating in Tennis | ITF
A robot referee can really keep its 'eye' on the ball
Tennis' highest-ranking umpire Soeren Friemel banned for 12 months over abuse of power claims
9,026 Tennis Referee Stock Photos, High-Res Pictures, and Images - Getty Images
Eva Asderaki - Wikipedia
Marijana Veljovic: Meet the 'super pretty' tennis umpire setting pulses racing at the Australian Open — RT Sport News
Tennis referee hi-res stock photography and images - Alamy
About the head referee - TENNIS
Officiating in Tennis | ITF
Are Referees Unfair to Female Players? | Psychology Today
Official (tennis) - Wikipedia
Stunning Serbian umpire Marijana Veljovic sends fans wild in Australian Open bust-up with Kyrgios | The US Sun
How To Get Started In A Tennis Official Role | LTA
A robot referee can really keep its 'eye' on the ball
Carlos Ramos, Umpire Known for Rigidity, Lands in U.S. Open Firestorm - The New York Times
