From A Bibliography of Alexandre Dumas père by Frank Wild Reed: It is exceedingly likely that these two studies were reprints of those which had been published earlier: "Hamlet" in "Le Monte-Cristo," Nos. for May 21st and 28th and June 4th, 1857, and "William Shakespeare," the introduction written in 1838 for Benjamin Laroche's translation of Shakespeare's plays.
The "Shakespeare" is now included in Vol. II, of the "Souvenirs Dramatiques," in the standard Calmann-Lévy edition (see page 427).
Original edition (of these two articles) : Paris, Michel Lévy Frères, 1 vol., 1867.