All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
Cristian Javier leads Astros to World Series history with combined no-hitter – Latino Sports
Houston Astros: 8 players don No. 21 on Roberto Clemente Day
Roberto Clemente Award - Wikipedia
Roberto Clemente: Baseball Rebel – Society for American Baseball Research
MLB's Puerto Rican-born players honor Roberto Clemente by wearing 21
Que Viva Clemente! Roberto Lives On in the Hearts of Latino Major Leaguers – Society for American Baseball Research
Roberto Clemente and Martin Luther King Jr.: In Service of Others – Society for American Baseball Research
NYSportsJournalism.com - MLB Accolades Commemorate Roberto Clemente Day - On Roberto Clemente Day, MLB Will Honor 50th Anniversary Of His Passing
Don Nottebart - Wikipedia
Divine intervention' and No. 21: The story of Roberto Clemente's 3,000th hit - The Athletic