Which men's singles has mixed doubles with Chen Hung-Ling Chou Chia-Chi?
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 "men_s_singles" FROM "previous_winners" WHERE "mixed_doubles"='chen hung-ling chou chia-chi';