Do MLB players have to wear numbers on their uniforms? - Quora
Now honoring No. 42: Jackie Robinson Day in majors - The San Diego Union-Tribune
Major League Baseball remembers No. 42 Jackie Robinson – The Denver Post
Uniform number (Major League Baseball) - Wikipedia
Yankees' Mariano Rivera Is the Last No. 42 - The New York Times
Mariners at forefront of establishing Jackie Robinson Day
Puerto Rican Twins don No. 21 in tribute to Roberto Clemente – Twin Cities
MLB to Celebrate Jackie Robinson Day Today – NBC Los Angeles
Jackie Robinson, Biography, Statistics, Number, Facts, & Legacy
Now honoring No. 42: Jackie Robinson Day in Major League Baseball - Deseret News
All players wearing 42 wrong way to honor Jackie