What year did Barry Sheene win the 125 cc?
CREATE TABLE "winners_of_the_swedish_motorcycle_grand_" (
  "year" text,
  "track" text,
  "125_cc" text,
  "250_cc" text,
  "report" text
);
SELECT "year" FROM "winners_of_the_swedish_motorcycle_grand_" WHERE "125_cc"='barry sheene';