MLB Umpires Missed 34,294 Pitch Calls in 2018. Time for Robo-umps?, BU Today
This day in sports: Jackie Robinson became first African-American major league baseball player in 1947
MLB names first Black and Latino born umpire crew chiefs – Pro Player Insiders
MLB appoints 1st black umpire crew chief
Art Williams made history as 1st Black umpire in National League
Emmett Ashford, Class of '41, to be honored by umpires nationwide
The lessons and legacy of Negro Leagues Baseball resonate beyond the diamond – Ewing Marion Kauffman Foundation
MLB's first black umpire broke the color barrier on Opening Day in D.C. 50 years ago - The Washington Post
Peter Dreier: Honoring Pasadena's Jackie Robinson – Pasadena Now
MLB makes history by naming its first black and Latino-born umpire crew chiefs
Local umpires awarded at inaugural Jimmy Lee Awards