Roberto Clemente - Wikipedia
Daily Sports Smile: 50 years after Roberto Clemente's death, MLB honors No. 21
Five Astros wear No. 21 on Roberto Clemente Day
Demilio: Roberto Clemente Day Serves as Another Reminder to Retire No. 21
Should Roberto Clemente's #21 Be Universally Retired Across MLB?
Mets, Pirates to Wear No. 21 on Clemente Day - Metsmerized Online
MLB expands list of who can wear No. 21 to honor Roberto Clemente on Sept. 15 - ESPN
Clemente Award winners will have 21 on caps for entire MLB career
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
For Many Latino Players, Roberto Clemente's Number Is Off Limits, Too - The New York Times
Curve Set to Retire No. 21 In Honor of Roberto Clemente
Pirates to wear No. 21 on Sept. 9 to honor Roberto Clemente - NBC Sports
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
Roberto Clemente Award winners to wear cap patch