Catalogue of Paintings by Joaquín Sorolla y Bastida. Exh. cat., Hispanic Society of America. New York, 1909, p. 89, no. 17, pl. 17, remarks that the ruins of the castle are on the left bank of the Tagus and notes that the Castle of San Servando was built by Alfonso VI to protect the convent of that name and the city.
"Accessions and Notes." Metropolitan Museum of Art Bulletin 17 (July 1922), p. 162.
Harry B. Wehle. The Metropolitan Museum of Art: A Catalogue of Italian, Spanish, and Byzantine Paintings. New York, 1940, pp. 306–7.