CREATE TABLE table_name_31 (opponent_in_final VARCHAR2, surface VARCHAR2, date VARCHAR2)

What is Opponent in Final, when Surface is 'Hard', and when Date is '13 January 1992'?
SELECT opponent_in_final FROM table_name_31 WHERE surface = "hard" AND date = "13 january 1992"
SELECT "opponent_in_final" FROM "table_name_31" WHERE "13 january 1992" = "date" AND "hard" = "surface"