Bar-Joseph U., A Question of Loyalty: Ashraf Marwan and Israel’s Intelligence Fiasco in the Yom Kippur War, “Intelligence and National Security” 2015, vol. 30, no. 5, pp. 667–685. https://doi.org/10.1080/02684527.2014.887632.

Błachut J., Czy „ciemna liczba przestępstw” istnieje? (Eng. Does a “dark crime figure” exist?), “Archiwum Kryminologii” 2007–2008, vol. 29–30, p. 75–80.

Flyvbjerg B., Pięć mitów o badaniach typu studium przypadku (Eng. Five myths about case study research), “Studia Socjologiczne” 2005, no. 2, pp. 41–69.

Ginor I., Remez G., Israel’s Best Spy – or a Master Double Agent? New light from the Soviet angle on the mystery of Ashraf Marwan, “The Journal of the Middle East and Africa” 2018, vol. 8, no. 4, pp. 383–396. https://doi.org/10.1080/21520844.2017.1409025.

Herrington S., Traitors Among Us: Inside the Spy Catcher’s World, San Diego 2000.

Hunter R.W., Hunter L.D., Spy Hunter: Inside the FBI Investigation of the Walker Espionage Case, Annapolis 1999.

Jonsson M., Espionage by Europeans: treason and counterintelligence in post-Cold war Europe, “Intelligence and National Security”. https://doi.org/10.1080/02684527.2023.2254020.

KGB Exploitation of Heinz Felfe. Successful KGB Penetration of Western Intelligence Ser- vice, Central Intelligence Agency, 12 IV 1978, https://www.cia.gov/readingroom/docs/FELFE%2C%20HEINZ%20%20KGB%20EXPLOITATION%20OF%20HEINZ%20FELFE_0001.pdf [accessed: 27 XI 2023].

Michálek L., Pokorný L., Transformation of the security and intelligence services in the Czech Republic, “Connections: The Quarterly Journal” 2019, vol. 18, no. 3–4, pp. 65–86. https://doi.org/10.11610/Connections.18.3-4.04.

Murphy D.E., KGB and MfS: Friendly enemies, “Intelligence and National Security” 1999, vol. 14, no. 3, pp. 228–234.

Penkovsky O., The Penkovsky papers, New York 1965.

Popplewell R.J., The KGB and the control of the Soviet bloc: The case of East Germany, “Intelligence and National Security” 1998, vol. 13, no. 1, pp. 254–285.

Scott L., Espionage and the cold war: Oleg Penkovsky and the Cuban missile crisis, “Intelligence and National Security” 1999, vol. 14, no. 3, pp. 23–47.

Stake R.E., Jakościowe studium przypadku (Eng. Qualitative case study), in: Metody badań jakościowych, vol. 1., N.K. Denzim, Y.S. Lincoln (eds.), Warszawa 2009, pp. 623–654.

Wise D., Tiger trap: America’s secret spy war with China, Boston 2011.

Internet sources

Annual Report on the activities of Latvian State Security Service (VDD) in 2022, Latvian State Security Service, https://vdd.gov.lv/uploads/materials/33/en/annual-report-2022.pdf [accessed: 27 XI 2023].

In the espionage case, Adamson is questioned about payments to his daughter and trips to the sauna in Moscow, Baltic News, 30 IV 2023, https://baltics.news/2023/04/30/in-the-espionage-case-adamson-is-questioned-about-payments-to-his-daughter-and-trips-to-the-sauna-in-moscow/ [accessed: 27 XI 2023].

Less than half of Russians in Latvia condemn Russia’s war in Ukraine: survey, Eng.LSM.lv, 7 VII 2022, https://eng.lsm.lv/article/society/society/less-than-half-of-russians-in-latvia-condemn-russias-war-in-ukraine-survey.a464423/ [accessed: 27 XI 2023].

Springe I., How Latvia is (not) catching Russian spies, re:baltica, 17 V 2018, https://en.rebaltica.lv/2018/05/how-latvia-is-not-catching-russian-spies/ [accessed: 27 XI 2023].