Zurich, 12 December 1955 - Institutional correspondence A letter from Klaus Herdeg to Willem Sandberg
New York, 14 August 1942 - Internal museum documents Elodie Courter Osborn's letter to Alfred H. Barr Jr.
New York, 20 August 1942 - Internal museum documents Elodie Courter Osborn's letter to Dorothy Dudley
<em>The New York Times</em>, New York, November 11, 1990, 1, 39 - Article “When Picasso Spooked the FBI”