Marlborough's Jim Reynolds calls it a career after 24 years as an MLB umpire - The Boston Globe
MLB umpire salary: How much do they take home on average?
MLB umpire job responsibilities
MLB Umpires Association, adamant that crews are simply upholding rule, address home-plate collision rule in statement - ESPN
MLB makes history with umpire crew chief appointments - Los Angeles Times
Long Island Baseball Umpires Organization - LIBUO
Atlantic League introduces 'robot umpires' to baseball - The Washington Post
Observations of Umpires at Work – Society for American Baseball Research
Umpire: What Is It? and How to Become One?
Gibson makes final call: MLB umpire retires after 24-year career, Sports
Umpire (baseball) - Wikipedia
To The Fence Umpires At The Local Little League: Be Quiet & Watch