Which Round has a Ranking of 2008 wta tour?
CREATE TABLE "top_10_wins_per_season" (
  "player" text,
  "ranking" text,
  "event" text,
  "surface" text,
  "round" text,
  "score" text
);
SELECT "round" FROM "top_10_wins_per_season" WHERE "ranking"='2008 wta tour';