What is the 250 cc with a year bigger than 1984?
CREATE TABLE "winners_of_the_yugoslavian_motorcycle_gr" (
  "year" real,
  "track" text,
  "250_cc" text,
  "500_cc" text,
  "report" text
);
SELECT "250_cc" FROM "winners_of_the_yugoslavian_motorcycle_gr" WHERE "year">1984;