CREATE TABLE table_57220 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

Which away team had a crowd bigger than 21,000?
SELECT "Away team" FROM table_57220 WHERE "Crowd" > '21,000'
SELECT "Away team" FROM "table_57220" WHERE "Crowd" > '21,000'