Rich tradition of retired numbers part of game's legacy
Giants coach Nick Ortiz campaigns for universally retiring Clemente's 21
MLB celebrates Roberto Clemente Day, ceremony at Citi Field
Roberto Clemente remains Latino legend 50 years after death
For Many Latino Players, Roberto Clemente's Number Is Off Limits, Too - The New York Times
Roberto Clemente Day: Pirates and Mets wear 21
Retire21 and farewell - Beyond the Box Score
Talkin' 21 Podcast Celebrates Roberto Clemente's legacy - Our Esquina
MLB celebrates Roberto Clemente Day, ceremony at Citi Field
Puerto Rican players follow Pirates' push to wear No. 21, celebrate Roberto Clemente
Mark Teixeira - Wikipedia
Roberto Clemente's legacy celebrated in N.Y., Puerto Rico