Yankees to retire Paul O'Neill's No. 21 on Aug. 21
Yankees Retired Numbers - Who Are The 22 Yankees Who Wore Them
Aaron Judge makes Yankees history with second 3-HR game of the season
New York Yankees: 5 numbers that need to be un-retired
As Paul O'Neill's No. 21 Is Retired, One Last Kick of a Water Cooler - The New York Times
As cases for Roy Halladay and Dick Allen point out, baseball's retired numbers are multiplying
New York Yankees Retired Numbers - Sports Illustrated
Yankees also retiring numbers for Bernie Williams and Jorge Posada
Here are the Yankees' 21 retired numbers Who belongs and who doesn't? Andy Pettitte, Jorge Posada, Bernie Williams, more
New York Yankees Retired Numbers - Sports Illustrated