Dowling 1973, p. 453. (EN) John Dowling, Buero Vallejo's Interpretation of Goya's Black Paintings, in Hispania, vol. 56, n. 2, maggio 1973, JSTOR339706.
Posèq 1999, p. 37. (EN) Avigdor Posèq, The Goat in Goya's Witches' Sabbaths, in Notes in the History of Art, vol. 18, n. 4, 1999, JSTOR23206811.