What date has a place of chernivtsi, and a race winners of etienne bax / kaspars stupelis? What
CREATE TABLE "2013" (
  "date" text,
  "place" text,
  "race_winners" text,
  "gp_winner" text,
  "source" text
);
SELECT "date" FROM "2013" WHERE "place"='chernivtsi' AND "race_winners"='etienne bax / kaspars stupelis';