ESPN - So, the New York Yankees are kind of running out of jersey options
Yankees Retired Numbers - Who Are The 22 Yankees Who Wore Them
Yankees Retired Numbers
List of Major League Baseball retired numbers - Wikipedia
Who were the first and last Yankees players to wear the retired numbers? - Pinstripe Alley
New York Yankees - Wikipedia
Yankees to retire Paul O'Neill's No. 21: See the complete list of retired numbers
What the Yankees' uniform number crunch could cost MLB's managers and coaches - The Athletic
Yankees Retired Numbers
Predicting the Next Retired Number for Every Team - The Crawfish Boxes