Pier della Vigna, Letters in 5 books: Critical edition of the oldest systematic collection, by Debora Riso. Introduction by Fulvio Delle Donne. SHARE Books, 2024. Accessed: Sep. 18, 2026. Available: https://www.fedoabooks.unina.it/index.php/fedoapress/catalog/book/978-88-98943-78-4