Umpire (baseball) - Wikipedia
MLB umpires should be mic'd up to explain reviews and ejections - Bleed Cubbie Blue
MLB Took a Slow Route to Developing a Speedier Game - WSJ
Report: MLB umps will use mics to relay results of reviews in 2020
American League wins 9th straight All-Star Game
This is why MLB umpires are wearing microphones this season
Locked in: MLB eager for openers
One change you might see at a Reds game this season
Angel Hernandez now interim umpire crew chief after opt outs –
Stanton, Buxton lead AL over NL in 9th straight All-Star win
Fernandomania' lives again at Dodger Stadium with retirement of Valenzuela's jersey
Umpires to announce replay reviews to fans