who is the constructor when the laps is less than 68, the grid is more than 20 and the driver is thierry boutsen?
CREATE TABLE "classification" (
  "driver" text,
  "constructor" text,
  "laps" real,
  "time_retired" text,
  "grid" real
);
SELECT "constructor" FROM "classification" WHERE "laps"<68 AND "grid">20 AND "driver"='thierry boutsen';