* Internet Encylclopedia of Philosophy on Universals* The Problem of Universals in Antiquity and the Middle Ages with an annotated bibliography* The Catholic Encyclopedia on "Nominalism, Realism, and Conceptualism"* The Friesian School on Universals
==External links==* Internet Encylclopedia of Philosophy on Universals* The Problem of Universals in Antiquity and the Middle Ages with an annotated bibliography* The Catholic Encyclopedia on "Nominalism, Realism, and Conceptualism"* The Friesian School on Universals