Zero or One Children ?
<!ELEMENT PLAYER (GIVEN_NAME, SURNAME, POSITION, GAMES, GAMES_STARTED, AT_BATS?, RUNS?, HITS?, DOUBLES?, TRIPLES?, HOME_RUNS?, RBI?, STEALS?, CAUGHT_STEALING?, SACRIFICE_HITS?, SACRIFICE_FLIES?, ERRORS?, WALKS?, STRUCK_OUT?, HIT_BY_PITCH?, WINS?, LOSSES?, SAVES?, COMPLETE_GAMES?, SHUT_OUTS?, ERA?, INNINGS?, EARNED_RUNS?, HIT_BATTER?, WILD_PITCHES?, BALK?,WALKED_BATTER?, STRUCK_OUT_BATTER?)