On what date did the away team score 13.13 (91) in front of a crowd larger than 15,601?
CREATE TABLE "round_20" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);
SELECT "date" FROM "round_20" WHERE "crowd">'15,601' AND "away_team_score"='13.13 (91)';