CREATE TABLE table_2263 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT)

Who were the writers of episode 20?
SELECT "Written by" FROM table_2263 WHERE "No. in season" = '20'
SELECT "Written by" FROM "table_2263" WHERE "No. in season" = '20'