See "Comments by President Salvador Allende on the Current Attitude of the Military Towards His Government and the Current Political Situation." United States, Central Intelligence Agency, September 6, 1973, available here.

Joan Garces has also published his recollections of the day of the coup, e.g. see Chapter 10 of Garcés, Joan E. Allende y la experiencia chilena: las armas de la política. Spain, Ariel, 1976. For a comprehensive recent account of the pro-Allende mobilizations on the day of the coup see Vidaurrázaga Manríquez, Ignacio. Martes once la primera resistencia. Chile, LOM Ediciones, 2021.

Monica Gonzales also recounts the details surrounding the operation in her book, see Chapter XXIV of González, Mónica. La conjura: los mil y un dias del golpe. Editorial Catalonia, 2013. Another account is provided in Whelan, James Robert. Allende, death of a Marxist dream. United States, Arlington House, 1981., pp. 28, 33-34, 77-80, 97. Despite its overall anti-Allende bent, the book is based on Whelan's first-hand interviews with those involved in the coup. 

For details on Letelier’s arrest on the day of the coup, see also McPherson, Alan. Ghosts of Sheridan Circle: How a Washington Assassination Brought Pinochet's Terror State to Justice. United States, University of North Carolina Press, 2019, pp. 35-36.

For Sergio Bitar's gripping account of the coup and its aftermath see Bitar, Sergio. Prisoner of Pinochet: My Year in a Chilean Concentration Camp. United States, University of Wisconsin Press, 2017.

See "Minutes of a Meeting of the Washington Special Actions Group." United States, Washington, September 12, 1973. Available here.

Roberto Simon's book on Brazil's aid to the coup-plotters remains indispensable: Simon, Roberto. O Brasil contra a democracia: a ditatura, o golpe no Chile e a guerra fria na America do Sul. Brazil, Companhia das Letras, 2021.

The extent of the US tech support to Chile’s police forces in the pre-Allende period can be gleaned from some of the USAID reports. As an example, see "Presentation to the Congress - FY 1968." United States, Agency for International Development, p. 98. Available here.

For details see, Katz, Paul. "Central American International Security Telecommunications Survey Report." United States, Agency for International Development, Washington, February 1964 (also cited in Schrader, Stuart. Badges Without Borders: How Global Counterinsurgency Transformed American Policing. United States, University of California Press, 2019), and "Proposed Central American International Security Telecommunications Network." United States, Department of State, March 23, 1964 (cited in Grandin, Greg. The Last Colonial Massacre: Latin America in the Cold War, Updated Edition. United Kingdom, University of Chicago Press, 2011), both on file with the author.

Stuart Schader discusses this in more depth in Schrader, Stuart. Badges Without Borders: How Global Counterinsurgency Transformed American Policing. United States, University of California Press, 2019, p. 183.

David Phillips discusses the CIA Ops Room dubbed "The Pit" in his autobiography: see Phillips, David Atlee. The night watch. New York, Atheneum, 1977, p. 147. On the Pit, also see Whipple, Chris. The Spymasters: How the CIA Directors Shape History and the Future. United Kingdom, Scribner, 2020, pp. 125-126. The Ops Room used in the Guatemalan operation described in Schlesinger, Stephen, et al. Bitter fruit: The story of the American coup in Guatemala. Cambridge, Harvard University Press, 2005, p. 103 – it mentions telexes as well.

See "The Administration: The Silent Service." Time, 24 Feb. 1967, available here.

This was related to us by the person in question, Fernando Shultz, during an interview.

The grim operations of the Caravan of Death are well-covered in González, Mónica. La conjura: Los mil y un dias del golpe. Editorial Catalonia, 2013, pp. 436-439.

Beer, Stafford. Letter to Heinz von Foerster. December 5, 1973. Stafford Beer collection, Box 69, Liverpool.

This was related to me by Tomas Kohn, a core member of the Cybersyn team, who joined Stafford during that visit.

"Nae Pasaran!", an excellent documentary about this matter, is available here.

See Saenz, Orlando. Testigo privilegiado: anécdotas, curiosidades, revelaciones, indiscresiones y peripecias de un espectador afortunado del pasado reciente. Chile, Arcus editorial, 2017, p. 89 (chapter "El Funeral"), where he also discusses the fate of the mysterious colonel who led the private intelligence network.