What rounds did Roy Salvadori drive for David Brown Corporation?
CREATE TABLE "teams_and_drivers" (
  "entrant" text,
  "constructor" text,
  "chassis" text,
  "engine" text,
  "tyre" text,
  "driver" text,
  "rounds" text
);
SELECT "rounds" FROM "teams_and_drivers" WHERE "entrant"='david brown corporation' AND "driver"='roy salvadori';