Black and Gold: Baseball should retire Roberto Clemente's No. 21
Roberto Clemente: Baseball Rebel – Society for American Baseball Research
MLB celebrates Roberto Clemente Day, ceremony at Citi Field
Demilio: Roberto Clemente Day Serves as Another Reminder to Retire No. 21
Carlos Delgado says MLB should retire Roberto Clemente's No. 21
Should Roberto Clemente's #21 Be Universally Retired Across MLB?
Should MLB retire Roberto Clemente's No. 21?
For Many Latino Players, Roberto Clemente's Number Is Off Limits, Too - The New York Times
Retiring Clemente's '21': True Recognition for Latinos in the Majors – Society for American Baseball Research
Campaign To Retire Roberto Clemente's No. 21 Throughout MLB Gains Traction