Which women was on the mixed doubles of tontowi ahmad lilyana natsir in 2011?
CREATE TABLE "previous_winners" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);
SELECT "women_s_singles" FROM "previous_winners" WHERE "mixed_doubles"='tontowi ahmad lilyana natsir' AND "year"=2011;