Perhaps you should try some spelling variations:
patients risk » patient risk, patients links, patients si
among users » among ers, among peers, among masters
wang tan » wang yan, wang ban, wang dan
tan yong » tan hong, tan kong, tan yang
can post » can cost, can postal, can boost
can past » can east, can fast, canal past
can lost » can cost, can lose, can boost

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

• Performing a fuzzy search may retrieve terms with similar spellings: wang tan yong ((((can post) OR (can past))) or (can lost)) patients risk among users ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: wang tan yong ((((can post) OR (can past))) OR (can lost)) patients risk among users ;*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "wang tan yong ((((can post) OR (can past))) or (can lost)) patients risk among users ;*".