What is the assembled date of the parliament with an unknown 2nd member who was elected in 1482/83?
CREATE TABLE "parliaments_of_king_edward_iv" (
  "summoned" text,
  "elected" text,
  "assembled" text,
  "dissolved" text,
  "1st_member" text,
  "2nd_member" text
);
SELECT "assembled" FROM "parliaments_of_king_edward_iv" WHERE "2nd_member"='unknown' AND "elected"='1482/83';