intelligence gathered by means interpersonal contact
- Advisors or foreign internal defence personnel working with the host nation forces or populations;
- Diplomatic reporting by accredited diplomats (e.g. military attachés);
- Espionage: secret reporting, using agents, couriers, cutouts;
- Military attachés: getting information is their job;
- Non-governmental organizations (NGOs);
- Prisoners of war (POWs) or other detainees;
- Routine patrolling (by military police, etc);
- Talking to travellers (e.g. the CIA Domestic Contact Service).
- Benedict, Ruth 1989. The Chrysanthemum and the Sword: patterns of Japanese culture. Mariner Books. ISBN 0-395-50075-3. Very widely used source for interpreting Japanese culture.
- Compos, Don The interrogation of suspects under arrest. (pdf), Studies in Intelligence, Central Intelligence Agency.  Archived 2020-10-17 at the Wayback Machine
- Walton, Douglas 2003. The interrogation as a type of dialogue. Journal of Pragmatics 35: 1771. 
- Skerker, Michael 2010. An ethics of interrogation. Chicago & London: University of Chicago Press.