What point is the lowest for listings of chassis labeled AGS JH23 before 1988?
CREATE TABLE "complete_formula_one_results" (
  "year" real,
  "chassis" text,
  "engine" text,
  "tyres" text,
  "points" real
);
SELECT MIN("points") FROM "complete_formula_one_results" WHERE "chassis"='ags jh23' AND "year"<1988;