lower right in graphite: RD84; lower left in graphite: SP
- Best Impressions: 35 Years of Prints and Sculpture from Gemini G.E.L., National Gallery of Art, Washington, 2001-2002.
- The Art of Collaboration: Works from the National Gallery of Art Gemini G.E.L. Archive, Academy Art Museum, Easton, Maryland, 9 Dec 2006 - 3 Feb 2007.
- Gemini G.E.L. Catalogue Raisonné, no. 1198.