References José López-Rey. "Maino y Velázquez, dos retratos de Felipe IV en el Metropolitan Museum de Nueva York." Colóquio no. 25 (1963), pp. 15–18, attributes it to Maino. José López-Rey. "A Portrait of Philip IV by Juan Bautista Maino." Art Bulletin 45 (1963), pp. 361–63, fig. 1. Shirley Sanford. Letter . February 14, 1964 [see old catalogue card], attributes it to Maino. Matías Díaz Padrón. "Gaspar de Crayer un pintor de retratos de los Austria." Archivo español de arte 38 (1965), pp. 238–39, fig. 3, attributes it to de Crayer. José López-Rey. "Sobre la atribución de un retrato de Felipe IV a Gaspar de Crayer." Archivo español de arte 39 (1966), pp. 195–96. Hans Vlieghe. "Caspar de Crayer als Bildnismaler, seine Entwicklung bis etwa 1630." Jahrbuch der kunsthistorischen Sammlungen in Wien , n.s., 27 (1967), pp. 99–101, fig. 91, supports the attribution to de Crayer. José López-Rey. Velázquez' Work and World . London, 1968, p. 42, pl. 37, as by Maino; dates it 1623–24, and calls the painting in the Palacio de Viana a mediocre imitation of it. Diego Angulo Íñiguez and Alfonso E. Pérez Sánchez. Historia de la pintura española: Escuela madrileña del primer tercio del siglo XVII . Madrid, 1969, p. 321, as by Maino. Hans Vlieghe. Gaspar de Crayer, sa vie et ses oeuvres . Brussels, 1972, vol. 1, pp. 258–59, no. A259; vol. 2, fig. 236. Priscilla E. Muller. "Maino, Crayer, Velázquez and a Miniature of Philip IV." Art Bulletin 58 (March 1978), pp. 87–89, fig. 3. José López-Rey. Velázquez: The Artist as a Maker, with a Catalogue Raisonné of His Extant Works . Lausanne, 1979, pp. 32, 158–59 n. 64, pl. 15, as by Maino, painted after January 1623. Julián Gállego. Diego Velázquez . Barcelona, 1983, p. 55, as by Maino. Walter A. Liedtke. Flemish Paintings in The Metropolitan Museum of Art . New York, 1984, vol. 1, pp. 32–34; vol. 2, pl. 17, suggests that this version of the portrait may be earlier than the one in the Palacio Viana, Madrid. Alfonso Rodríguez G. de Ceballos in Juan Bautista Maíno, 1581–1649 . Exh. cat., Museo Nacional del Prado. Madrid, 2009, pp. 190, 213, 307, fig. 34.8 (color). Leticia Ruiz Gómez in Juan Bautista Maíno, 1581–1649 . Exh. cat., Museo Nacional del Prado. Madrid, 2009, pp. 197–98, 309–10, fig. 37.1 (color detail). Leticia Ruiz Gómez. E-mails to Keith Christiansen . April 1 and April 3, 2009, reconsiders her attribution of this painting to Maino [Ref. 2006] and restores it to de Crayer, noting that he had a moment in the 1620s in which his style was quite close to that of Maino.