Milan, 4 August 1953 - Institutional correspondence A letter from Fernanda Wittgens to Willem Sandberg, dated 4 August 1953
Milan, 12 August 1953 - Institutional correspondence Fernanda Wittgens' letter to Willem Sandberg, dated 12 August 1953
Milan, 7 October 1953 - Institutional correspondence A letter from Fernanda Wittgens to Willem Sandberg, dated 7 October 1953
ca. 1952–1956 - Internal museum documents Publicity report for the exhibition Studies for Guernica by the School of Fine and Applied Arts, Columbus, Ohio, addressed to the Travelling Exhibitions Department at the Museum of Modern Art, New York