What is the Bulgarian Commander in Autumn 1040 at the Battle of Thessalonica?
CREATE TABLE "medieval_bulgarian_army" (
  "battle" text,
  "date" text,
  "bulgarian_commander" text,
  "byzantine_commander" text,
  "result" text
);
SELECT "bulgarian_commander" FROM "medieval_bulgarian_army" WHERE "battle"='battle of thessalonica' AND "date"='autumn 1040';