It's time for Roberto Clemente's No. 21 to be retired across baseball - Bucs Dugout
To Pirates catcher Michael Perez, wearing No. 21 'very special
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
Nats DH Cruz, other Clemente Award winners wear '21' on caps
Cincinnati Reds: Best player in team history to wear No. 21
Angels news: Remembering Roberto Clemente - Halos Heaven
The only day MLB players can wear No. 42? Jackie Robinson Day
Uni Watch - MLB firsts and lasts - ESPN
MLB expands list of who can wear No. 21 to honor Roberto Clemente on Sept. 15 - ESPN
Rays again lean into Roberto Clemente Day event
Uniform number (Major League Baseball) - Wikiwand
MLB Ballplayers Can Now Wear #21 Patch on Ballcaps and Helmets – SportsLogos.Net News
Blue Jays players, personnel wear No. 21 in honour of Roberto Clemente