1. Alford, S. (2011, June 12). Eritrea Frees Four British Men Accused of Spying. The Times.
https://www.thetimes.co.uk/article/eritrea-frees-four-british-men-accused-of-spying-rbpxr0sj8kh
. Accessed: 4 January 2020.
2. Ambrey. (2020).
https://ambrey.com
. Accessed: 6 January 2020.
3. Arnold, G. (1999). Mercenaries: The Scourge of the Third World. London: Macmillan Press.
4. ASIS—ASIS Commission on Standards and Guidelines. (2012). Standard (PSC.1): Management System for Quality of Private Security Company Operations-Requirements with Guidance. Alexandria, VA: ASIS International.
5. Avant, D. D. (2005). The Market for Force. Cambridge: Cambridge University Press.