What is the earliest year a chassis of ferrari 312t and results of 31 points occurred?
CREATE TABLE "complete_formula_one_world_championship_" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" text
);
SELECT MIN("year") FROM "complete_formula_one_world_championship_" WHERE "chassis"='ferrari 312t' AND "points"='31';