Carrie E. Benes: Urban legends: Civic identity and the classical past in northern Italy, 1250–1350. Pennsylvania State University Press, University Park 2011, ISBN 978-0-271-03765-3, S. 89–90 (books.google.de).
John T. Paoletti, Gary M. Radke: Siena: City of the Virgin. In: Art in Renaissance Italy. Laurence King Publishing, London 2005, ISBN 1-85669-439-9, S. 99 (books.google.de).
