Petrilli, S., & Ponzio, A. Peirce and medieval semiotics: Susan Petrilli. Augusto Ponzio. Peirce's doctrine of signs : theory, applications, and connections.(1996).

Petrilli, Susan, and Augusto Ponzio. "Peirce and Medieval Semiotics: Susan Petrilli. Augusto Ponzio." Peirce's Doctrine of Signs : Theory, Applications, and Connections.(1996) .

Petrilli, Susan, and Augusto Ponzio. "Peirce and Medieval Semiotics: Susan Petrilli. Augusto Ponzio." Peirce's Doctrine of Signs : Theory, Applications, and Connections.(1996), .