upper right, in block: 4-'35 MCE; lower left, in pencil: MCEscher
- The Worlds of M.C. Escher: Nature, Science, and Imagination, North Carolina Museum of Art, Raleigh, 2015.
- Bool, F.H. et al. M.C. Escher: His Life and Complete Graphic Work. Amsterdam: Meulenhoff, 1981; English-language edition, New York: Harry N. Abrams, 1982.