Include quotation marks around your search terms when you want to find them together, ie. "Physician's Assistant"
Hairdresser working on young woman's hair. Photography. Encyclopædia Britannica ImageQuest. Web. 7 Apr 2015.
http://quest.eb.com/search/154_2883141/1/154_2883141/cite
By CPL Clay Beyersdorfer [Public domain], via Wikimedia Commons