• M. Clagett, The Science of Mechanics in the Middle Ages (Madison: 1959).

• R.C. Dales, The Scientific Achievement of the Middle Ages (Philadelphia: 1973).

• C.H. Leijenhorst et al. (eds), The Dynamics of Aristotelian Natural Philosophy from Antiquity to the Seventeenth Century (Leiden: 2002).

• A. Maier, Studien zur Naturphilosophie der Spätscholastik, 5 vols (Rome: 1949-68).

• E.D. Sylla, “The Oxford Calculators’ Middle Degree Theorem in Context,” Early Science and Medicine 15 (2010), 338-70.

• E.D. Sylla, The Oxford Calculators and the Mathematics of Motion (New York: 1991).

• C. Wilson, William Heytesbury: Medieval Logic and the Rise of Mathematical Physics (Madison: 1956).

Stanford Encyclopedia: William Heytesbury

Stanford Encyclopedia: Richard Kilvington