Which season has a Staffel E of Stahl Riesa?
CREATE TABLE "1971_1984" (
  "season" text,
  "staffel_a" text,
  "staffel_b" text,
  "staffel_c" text,
  "staffel_d" text,
  "staffel_e" text
);
SELECT "season" FROM "1971_1984" WHERE "staffel_e"='stahl riesa';