Pirates will honor Roberto Clemente by wearing his No. 21 on their jerseys - ESPN
Uniform number (Major League Baseball) - Wikipedia
Pittsburgh Pirates each don No. 21 to honor Roberto Clemente - ESPN
MLB's Pirates will honor Roberto Clemente by wearing his number
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Members of Red Sox wear No. 21 with pride on Roberto Clemente Day - The Boston Globe
Pirates, MLB honour 'the Great One' Roberto Clemente
Pittsburgh Pirates, New York Mets players, coaches to all wear No. 21 on Roberto Clemente Day - ESPN
MLB celebrates former Pirates great Roberto Clemente Day
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
21: The Story of Roberto Clemente: 9781560978923: Santiago, Wilfred: Books
Pirates to once again wear No. 21 for Roberto Clemente Day
ESPN: MLB to allow Pirates, Puerto Rican players, award nominees to wear No. 21 on Roberto Clemente Day
MLB's Puerto Rican-born players honor Roberto Clemente by wearing 21
Pittsburgh Pirates to wear No. 21 on Roberto Clemente Day
