Who won the mens singles when lau sui fei won the womens singles?
CREATE TABLE "polish_open" (
  "year_location" text,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text
);
SELECT "mens_singles" FROM "polish_open" WHERE "womens_singles"='Lau Sui Fei';