Franz Landsberger. “The Origin of the Winged Angel in Jewish Art,” Hebrew Union College Annual 20 (1947), pp. 227–254; Marie Thérèse D’Alverny, “Les anges et les jours,” Cahiers archéologiques 9 (1957), pp. 271–300. See Weitzmann and Kessler, The Cotton Genesis, 40, for differing depiction of angels in the Cotton Genesis. In 1 Enoch 61:1, according to Ephraim Isaac, the version with no wings is older than the one with wings; in James Charlesworth, ed., The Old Testament Pseudepigrapha (Garden City, NY: Doubleday, 1983), vol. 1, p. 7.