Bonn, 16 February 1956 - Institutional correspondence Antonio Mª Aguirre's letter to Alberto Martín-Artajo Álvarez
<em>The New York Times</em>, New York, November 11, 1990, 1, 39 - Article “When Picasso Spooked the FBI”
New York, 22 February 1979 - Institutional correspondence Michael Blackwood's letter to Louise Kreisberg