Ferdinando Bologna. Letter to Everett Fahy. February 19, 1969, calls it an autograph "bozzetto" for the picture in the Pignatelli collection.
Federico Zeri with the assistance of Elizabeth E. Gardner. Unpublished manuscript for catalogue of Neapolitan paintings in The Metropolitan Museum of Art. [ca. 1970], as "Diego Pignatelli d'Aragona," Prince of the Holy Roman Empire, Marquess of Valle de Oxaca, later Duke of Terranova and Monteleone; note that the sitter was the oldest son of Niccolò Pignatelli (1648–1730), Viceroy of Sardinia and Sicily, and Giovanna II Aragona Pignatelli Cortes; point out that Don Diego wears the collar of the Order of the Golden Fleece and stands near a table decorated with the Pignatelli coat of arms; consider this work, "executed on a dark reddish-brown ground," the preliminary sketch for a larger canvas by Solimena now owned by the descendents of Pignatelli in Rome; on stylistic grounds, date both works about 1730, the year that Don Diego inherited the family titles.
Oil Sketches by 18th Century Italian Artists from New York Collections. Exh. cat., The Metropolitan Museum of Art. [New York], 1971, p. 7, no. 24, calls this study "Diego Pignatelli d'Aragona, Duke of Terranova and Monteleone"; compares it to the finished portrait in Rome, noting minor alterations in composition such as the position of the fingers and the buildings in the background.
Burton B. Fredericksen and Federico Zeri. Census of Pre-Nineteenth-Century Italian Paintings in North American Public Collections. Cambridge, Mass., 1972, pp. 190, 516, 609.
Nicola Spinosa in Civiltà del '700 a Napoli, 1734–1799. Exh. cat., Museo Nazionale di Capodimonte, Naples. Florence, 1979, vol. 1, p. 178, identifies it as a preparatory sketch for the portrait of Pignatelli (1687–1750) in Rome; places it at the very end of 1731 and beginning of 1732, pointing out that the sitter wears the attire and collar of the Order of the Golden Fleece given to him by Emperor Charles VI of Habsburg in December 1731.
John T. Spike. Baroque Portraiture in Italy: Works from North American Collections. Exh. cat., John and Mable Ringling Museum of Art. Sarasota, 1984, p. 178–79, no. 68, ill., describes it as a preparatory sketch for one of Solimena's "masterpieces of portraiture"; accepts Spinosa's date of 1731–32 for the finished portrait and our bozzetto [see Ref. Spinosa 1979]; notes that by the fourth decade of the 18th century the "attributes and ambience of the sitter are as important to the interpretation as is his likeness"; suggests that Solimena "made use of a preparatory sketch in order to assist his comprehension of the space and the arrangement of lights and darks in the full-length portrait".
Nicola Spinosa. Pittura napoletana del Settecento: dal Barocco al Rococò. Naples, 1986, pp. 115, no. 48, 208, fig. 55 (color), as "Il principe Diego Pignatelli"; places this work in the genre of the Neapolitan "ritratto di Stato," also practiced by De Mura and il Bonito.
Richard Brilliant in Likeness and Beyond: Portraits from Africa and the World. Exh. cat., Center for African Art. New York, 1990, pp. 14–15, 18, 20–21, 138–39, no. 79, ill. (color), as "Don Diego Pignatelli d'Aragona".
Giuliano Briganti, ed. La pittura in Italia: il Settecento. Milan, 1990, vol. 2, fig. 671, as "Il principe Diego Pignatelli".
Wolfgang Prohaska in Barock in Neapel: Kunst zur Zeit der österreichischen Vizekönige. Exh. cat., Kunstforum der Bank Austria, Vienna. Naples, 1993, pp. 274–75, no. 67, ill. (color), notes that Diego Pignatelli was such a fervent supporter of the Habsburgs that he was forced to flee to Calabria in 1744; mentions an engraving by the painter Domenico Mondos that closely follows our image, which appears as the frontispiece to a 1752 commemorative volume on Pignatelli.