CREATE TABLE table_28044 ("Series no." FLOAT, "No. in season" FLOAT, "Title" TEXT, "Written by" TEXT, "Directed by" TEXT, "Original air date" TEXT, "U.S. viewers  ( millions ) " TEXT)

Who wrote the episode where the original air date is july20,2007?
SELECT "Written by" FROM table_28044 WHERE "Original air date" = 'July20,2007'
SELECT "Written by" FROM "table_28044" WHERE "Original air date" = 'July20,2007'