Why are there still umpires in Major League Baseball? Why can't it all be automated? - Quora
What is a strike in baseball? Robots, rule book and umpires view it differently
Explaining ball-strike challenge system
Can computers call 'em better than the umps? - The Boston Globe
BenFred: MLB umpires, you're out. It's time for an automated strike zone.
Jamie Samuelsen: Time to take balls and strikes away from umpires
Computer to call balls and strikes in minor league
Worcester Red Sox are preparing for robotic ball-strikes system coming
MLB umpires agree to allow computerized strike zone: report – New York Daily News