TSN Archives: Baseball Mourns Loss of Bucs Star Clemente (Jan. 13, 1973, issue)
Roberto Clemente: Cincinnati Reds' José De León wants MLB to retire 21
Pirates will honor Roberto Clemente by wearing his No. 21 on their jerseys - ESPN
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
Roberto Clemente remains Latino legend 50 years after death
OTL: The enduring mystery of Roberto Clemente's bat - ESPN
Should MLB retire Roberto Clemente's No. 21?
Roberto Clemente's Year in the Dodgers Organization – Society for American Baseball Research
Roberto Clemente - Wikiquote
OTL: The enduring mystery of Roberto Clemente's bat - ESPN
Tell MLB to retire Roberto Clemente's number
Roberto Clemente: Cincinnati Reds' José De León wants MLB to retire 21
Yankees retire Paul O'Neill's No. 21 jersey, Brian Cashman booed