CREATE TABLE "table1_28140578_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" real
);

Question: Who wrote episode number 19 in the series?
SQL: SELECT "written_by" FROM "table1_28140578_1" WHERE "no_in_series"=19;