Which Round has a Method of ko, and a Date of 1958?
CREATE TABLE "amateur_boxing_record_roy_scheider" (
  "result" text,
  "opponent" text,
  "method" text,
  "date" text,
  "round" real
);
SELECT MIN("round") FROM "amateur_boxing_record_roy_scheider" WHERE "method"='ko' AND "date"='1958';