When the crowd was over 16,000 people and south melbourne was the away team, what date was the game?
CREATE TABLE "round_4" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);
SELECT "date" FROM "round_4" WHERE "crowd">'16,000' AND "away_team"='south melbourne';