Perhaps you should try some spelling variations:
ratings risk » patients risk
among east » among breast, among ers, among health
yan yang » yang yang, dan yang, tan yang
yao yang » yang yang
can post » can lost, can past, can postal
can cost » can costa, can lost, chain cost
wang » wing, wan, lang

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "wang ((yan yang) OR (yao yang)) ((can post) OR (can cost)) ratings risk among east ;~".
• Adding a wildcard symbol may retrieve word variants: wang ((yan yang) OR (yao yang)) ((can post) OR (can cost)) ratings risk among east ;*.