Maulfelt, T., & Helm, A. v. d. (2014). Questiones libri Porphirii: Thomas Manlevelt. A crit. ed. with introd. and indices by Alfred van der Helm. Brill.

Maulfelt, Thomas, and Alfred van der Helm. Questiones Libri Porphirii: Thomas Manlevelt. A Crit. Ed. with Introd. and Indices by Alfred Van Der Helm. Leiden ; Boston: Brill, 2014.

Maulfelt, Thomas, and Alfred van der Helm. Questiones Libri Porphirii: Thomas Manlevelt. A Crit. Ed. with Introd. and Indices by Alfred Van Der Helm. Brill, 2014.