Early Flemish Painting p. 72-73; Fred S. Kleiner and Christin J. Mamiya, Gardner's Art Through the Ages, 12th ed., vol 2 (Belmont, CA: Thomson/Wadsworth, 2005), 555; James Snyder, Northern Renaissance Art, 2nd ed., revised by Larry Silver and Henry Luttikhuizen (Upper Saddle River, NJ: Prentice Hall, 2005), 126-128.