Perhaps you should try some spelling variations:
ratings risk » patients risk
can costa » can cost, can postal, da costa
can close » can lose, a close, can cause
among ers » among peers, among users, among east
wang tan » wang yan, wang ban, wang dan
tan yang » dan yang, tan ying, tan yong
can lost » can cost, can lose, can post

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 tan yang ((((can lost) OR (can close))) OR (can costa)) ratings risk among ers ;~.
• Adding a wildcard symbol may retrieve word variants: wang tan yang ((((can lost) or (can close))) or (can costa)) ratings risk among ers ;*.