Discusses that the 1609 Quatro of `Shakespeare's Sonnets' cataloguing William Shakespeare's sonnets is considered by most 19th- and 20th- century commentators as an unauthorized publication. Description of the documentation; Composition of the Quatro sequence; Rhyme-word linking method used; Flaws of the `Dark Lady' section; Cataloguing of Helen Vendler in her book `Shakespeare's Sonnets'.