Umpire (baseball) - Wikipedia
How Umpires Work
The story of Canada's lone MLB umpire: From Saskatchewan to The Show
MLB makes history with umpire crew chief appointments - Los Angeles Times
Umpire (baseball) - Wikipedia
Five Minutes with Gerry Davis - Little League
Observations of Umpires at Work – Society for American Baseball Research
The MLB Umpires Association is a flawed and opaque organization - Bleed Cubbie Blue
A New Study Shows Umpire Discrimination Against Non-White Players - Baseball ProspectusBaseball Prospectus
Umpire (baseball) - Wikipedia
MLB Umpires Association, adamant that crews are simply upholding rule, address home-plate collision rule in statement - ESPN
Major League Baseball umpires: Danger zone ahead?
10 Secrets of MLB Umpires