Confrontations with Aggression and Mental Health Problems in Police Officers: The Role of Organizational Stressors, Life-events and Previous Mental Health Problems Publication Type: Journal Article Authors: Peter G. van der Velden; Rolf Kleber; Linda Grievink; Joris C. Yzermans Source: Psychological Trauma: Theory, Research, Practice, and Policy, Volume 2, Issue 2, p.135-144 (2010)