1. Avant D 2005. The market for force: The consequences of privatizing security. Cambridge: Cambridge University Press.
2. Bailes, A.J.K. and Holmqvist, C., 2007. The increasing role of private military and security companies. European Parliament, Directorate-General for External Policies of the Union.
3. Barrie, D., et al., 2018. Protecting Europe: meeting the EU’s military level of ambition in the context of Brexit. The International Institute for Strategic Studies and the German Council on Foreign Relations. Available from: https://dgap.org/system/files/article_pdfs/protecting_europe.pdf.
4. Private military contractors’ financial experiences and incentives;Batka C.;Defense & security analysis,2020
5. Examining the positive and negative aspects of US military/contractor bonds in the operational environment;Batka C.;Journal of political & military sociology,2021