Pressure to make journalists reveal their sources of information may take the form of arrest, trial and imprisonment or general intimidation. Recent examples of threats to journalistic immunity have occurred in USA court cases, with convictions against journalists for the publication of the Pentagon Papers. In countries where political censorship is heavy, journalists may be imprisoned and tortured for subversive activities. Information may concern crime, corruption or other injustices, or be akin to espionage; and the possibility that sources would be revealed would risk making it more difficult or even impossible to obtain this information. The public would therefore be deprived of knowledge about matters which might concern them directly or indirectly.