lower right, on stone: I-'30 MCE / STAMPATO.I.CRAIA. ROMA; lower left, in pencil: MC Escher No. 26/45
- 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.