APA Style is from the American Psychological Association. It is a very widely used style in the social sciences--not just in psychology. It is probably the most commonly used style on campus.
Post-traumatic stress disorder treatment. Virtual reality simulator being used by the US military to help with the treatment of post-traumatic stress disorder (PTSD).
Post-traumatic stress disorder treatment. Photography. Britannica ImageQuest. Encyclopædia Britannica, Inc., 25 May 2016.
http://quest.eb.com/search/132_1311114/1/132_1311114/cite. Accessed 24 Aug 2016.