Bill Russell is third athlete to have number retired league-wide
Uniform number (Major League Baseball) - Wikipedia
History of retired numbers dates back to Lou Gehrig Day
Pittsburgh Pirates - Wikipedia
Derek Jeter's No. 2, Last of Yankees' Single Digits, to Be Retired
Lakers News: First Great Lakers Center Will Have Jersey
Retired numbers in Phillies team history
NBA -- Inside the numbers on the NBA's retired numbers - ESPN
LeBron James will join this list of NBA players with numbers
Every MLB team's retired numbers
Every MLB team's retired numbers
Should Tom Brady's #12 jersey number be retired league-wide