In the circuit Showevent Olympiastadion München, where the winning driver is Bruno Spengler, what is the pole position?
CREATE TABLE "race_calendar_and_results" (
  "round" text,
  "circuit" text,
  "date" text,
  "pole_position" text,
  "fastest_lap" text,
  "winning_driver" text,
  "winning_team" text
);
SELECT "pole_position" FROM "race_calendar_and_results" WHERE "winning_driver"='Bruno Spengler' AND "circuit"='Showevent Olympiastadion München';