Input (grade 7): (Okkonen, p. 36, p. 120) In 1929, numbers were first added on the backs of uniforms by the New York Yankees and the Cleveland Indians. By 1932, all major league baseball teams had numbers on their players' uniforms.
Output (grade 9): In 1929, numbers were first added on the backs of baseball uniforms by the New York Yankees and the Cleveland Indians baseball teams.