"Inscripción de construcción del rey Recesvinto" [Construction inscription of King Recesvinto] (in Spanish). Translated by Palol, Pedro de. National Archaeological Museum of Spain. Retrieved 2017-11-10. (The date 699 corresponds to 661 because of the difference of 38 years between the Spanish era calendar and the anno Domini calendar.)
Wright, George R.H. (2000). Ancient Building Technology, Vol 1: Historical Background. Technology and Change in History. Leiden, The Netherlands: E.J. Brill. Illustration 54. ISBN978-90-04-09969-2. OCLC490715142.
