upper center in green ink, circled: 4; lower right in black ink: system / [6-8]; lower left verso in graphite: T640-x-1971
- M.C. Escher: A Centennial Tribute, National Gallery of Art, Washington; San Diego Museum of Art; The Chrysler Museum of Art, Norfolk, 1997-1999.
- "M.C. Escher", Knoxville Museum of Art, 2000.