Perhaps you should try some spelling variations:
present challenges » current challenges, assessment challenges
recent challenges » recent changes, treatment challenges, emergent challenges
wang yang » wang yan, wang liang, wang yanling
hong ghi » zhong zhi, hong g, hong hai
yang xi » yang di, yang yi, yang jui
ng a » lng a, ngo a, png a

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((wang yang) or (yang xi))ng a 4 ((recent challenges) OR (present challenges)) tan hong ghi ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((wang yang) OR (yang xi))ng a 4 ((recent challenges) OR (present challenges)) tan hong ghi ;*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((wang yang) or (yang xi))ng a 4 ((recent challenges) OR (present challenges)) tan hong ghi ;*".