Guiseppe Zarlino, The Art of Counterpoint , Part III of Le Istitutioni harmoniche, 1558. Trans. Guy A. Marco and c. V. Palisca. New Haven: Yale University Press, 1968; N.Y.: w. w. Norton, 1976; N.Y.: Da Capo Press, 1983. *Especially III, 42, pp. 91-102.
James Haar, "Zarlino's Definition of Fugue and Imitation," Journal of the American Musicological Society 24/2 (1971), 226-254.
Jairo Moreno, "Zarlino: Instituting Knowledge in the Time of Correspondences," Musical Representations, Subjects, and Object: The Construction of Musical Thought in Zarlino, Descartes, Rameau, and Weber Bloomington: University of Indiana Press, 2004, 26-49.