History of retired numbers dates back to Lou Gehrig Day
New York Yankees Retired Numbers - Sports Illustrated
Yankees, Eager to Retire Numbers, Subtract Options for Current Players - The New York Times
Lou Gehrig MLB Career and Early Life, The Iron Horse
Baseball In Pics on Instagram: “Lou Gehrig had his number 4 retired, and gave one of the great speeches in history on “Lou Gehrig Day”, July 4, 1939.”
Lou Gehrig Day's reminder of why your help is still needed National News - Bally Sports
MLB & Dodgers Celebrating 2nd Annual Lou Gehrig Day
Lou Gehrig - Wikipedia
Yankees retired numbers