Who won Men's singles the year that Hilde Themel won Women's singles?
CREATE TABLE "previous_winners" (
  "year" text,
  "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 "women_s_singles"='hilde themel';