CREATE TABLE table_73475 ("No. in series" TEXT, "No. in season" TEXT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT, "U.S. viewers  ( millions ) " TEXT)

Name the production code by paul lieberstein
SELECT "Production code" FROM table_73475 WHERE "Written by" = 'Paul Lieberstein'
SELECT "Production code" FROM "table_73475" WHERE "Written by" = 'Paul Lieberstein'