Which Source model has a Release date of 1992-04-06?
CREATE TABLE "dos_shells" (
  "name" text,
  "release_date" text,
  "latest_version" text,
  "status_support" text,
  "source_model" text,
  "architecture" text,
  "target_market" text
);
SELECT "source_model" FROM "dos_shells" WHERE "release_date"='1992-04-06';