The Cubs should retire several more jersey numbers - Bleed Cubbie Blue
History of retired numbers dates back to Lou Gehrig Day
Yankees Retired Numbers - Who Are The 22 Yankees Who Wore Them
Where Derek Jeter ranks among Yankees' retired single-digit numbers
The only day MLB players can wear No. 42? Jackie Robinson Day
NY Yankees royalty honored as Paul O'Neill's No. 21 is retired
New York Yankees retired Paul O'Neill's No. 21 jersey
All-time best Yankees by jersey number (1-33)
Yankees retired numbers: A look at all of the jersey numbers players cannot wear in the Bronx
Yankees Retired Numbers Quiz
Yankees' Mariano Rivera Is the Last No. 42 - The New York Times
The second-best Yankee to wear each retired number - Part One - Pinstripe Alley
New York Yankees Retired Numbers - Sports Illustrated
Yankees retired numbers: A look at all of the jersey numbers players cannot wear in the Bronx
NY Yankee Paul O'Neill's No. 21 to be retired on Aug. 21