What series did the racer earn 68 points in?
CREATE TABLE "career_results" (
  "season" real,
  "series" text,
  "team" text,
  "races" real,
  "wins" real,
  "poles" real,
  "f_laps" real,
  "podiums" real,
  "points" text,
  "position" text
);
SELECT "series" FROM "career_results" WHERE "points"='68';