CREATE TABLE table_13670 ("Title" TEXT, "Director" TEXT, "Writer" TEXT, "Original airdate" TEXT, "Prod. Code" TEXT)

Who wrote 'The Six Stages of Marshall'?
SELECT "Writer" FROM table_13670 WHERE "Title" = 'the six stages of marshall'
SELECT "Writer" FROM "table_13670" WHERE "Title" = 'the six stages of marshall'