Perhaps you should try some spelling variations:
patients risk » patient risk, patients links, patients si
yang iran » yang dean, yang fan
iran cost » urban cost, iran case, can cost
yan yang » yang yang, yao yang, dan yang
gong hui » tong hui, tong shui, wang hui
hong hai » shang hai, zhong tai, dang hai
wang » wing, wan, lang

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: wang yan yang iran cost ((ratings risk) OR (patients risk)) ((gong hui) OR (hong hai)) ;~.
• Adding a wildcard symbol may retrieve word variants: wang yan yang iran cost ((ratings risk) or (patients risk)) ((gong hui) or (hong hai)) ;*.