Yankees to retire Paul O'Neill's No. 21: See the complete list of retired numbers
How many jersey numbers do the Yankees have left? - Deseret News
New York Yankees retire Paul O'Neill's No. 21; GM Brian Cashman, owner Hal Steinbrenner booed by fans - ESPN
New York Yankees retired Paul O'Neill's No. 21 jersey
Yankee Retired Numbers: The All-Time Numerical Lineup of Yanks
Paul O'Neill stunned Yankees are retiring his number
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Yankees Retired Numbers - Who Are The 22 Yankees Who Wore Them