The "Head of State" episode was authored by which person?
CREATE TABLE "table1_15861819_1" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "originalairdate" text,
  "tv_broadcast" text
);
SELECT "written_by" FROM "table1_15861819_1" WHERE "title"='\"Head of State\"';