How Paul O'Neill Stacks Up Against the Other Yankees With Retired Numbers
New York Yankees history: Paul O'Neill's number 21 must be retired
Appreciating the retired single-digit numbers of the New York Yankees
Yankees Retired Numbers - Who Are The 22 Yankees Who Wore Them
Zero single-digit numbers in the Bronx? Actually, there's still one left - ESPN
Who were the first and last Yankees players to wear the retired numbers? - Pinstripe Alley
Yankee Retired Numbers: The All-Time Numerical Lineup of Yanks
The All-Unretired Yankees, Bronx Pinstripes
Yankees retired numbers: Paul O'Neill latest to be added to list
Here are the Yankees' 21 retired numbers Who belongs and who doesn't? Andy Pettitte, Jorge Posada, Bernie Williams, more
Hideki Matsui re-signs with Yankees, then retires
New York Yankees retired numbers: Is team too generous? - Sports Illustrated