What is Opponent in Final, when Surface is "Hard", and when Date is "13 January 1992"?
CREATE TABLE "wins_15" (
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_final" text,
  "score_in_final" text
);
SELECT "opponent_in_final" FROM "wins_15" WHERE "surface"='hard' AND "date"='13 january 1992';