Name the lowest Wins which has Points of 28, and a Year smaller than 1972?
CREATE TABLE "grand_prix_motorcycle_racing_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "wins" real
);
SELECT MIN("wins") FROM "grand_prix_motorcycle_racing_results" WHERE "points"=28 AND "year"<1972;