(in Spanish) Fundacion Jose Guillermo Carrillo, Gustavo Machado Morales, Diccionario Histórico Biográfico Editado por la Fundación Polar Caracas, Venezuela
nsa.gov
"Venona"(PDF). National Security Agency. 6 July 1944. Archived from the original(PDF) on 18 September 2013. Retrieved 14 March 2014.