Roxbury, 22 November 1955 - Institutional correspondence Alexander Calder's letter to Willem Sandberg, dated 22 November 1955
Roxbury, 12 January 1956 - Institutional correspondence Alexander Calder's letter to Willem Sandberg, dated 12 January 1956
www.gregorysholette.com, 2011 - Article A Collectography of PAD/D Political Art Documentation and Distribution: A 1980s Activist Art and Networking Collective