Perhaps you should try some spelling variations:
present challenges » current challenges, assessment challenges
challenges m » challenges 1, challenges 3, challenges 5
wang yang » wang yan, wang liang, wang yanling
a present » _ present, 3 present, 2 present
zhong tai » hong tan, zhong zhi
hong hai » shang hai, dang hai, hong tan
yang yi » yang di, yang xi, yang jui
ng y » ng _, g y, na y
y a » y la

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 yi))ng y a present challenges m ((hong hai) OR (zhong tai)) ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((wang yang) OR (yang yi))ng y a present challenges m ((hong hai) OR (zhong tai)) ;.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((wang yang) or (yang yi))ng y a present challenges m ((hong hai) OR (zhong tai)) ;".
• Adding a wildcard symbol may retrieve word variants: ((wang yang) or (yang yi))ng y a present challenges m ((hong hai) OR (zhong tai)) ;*.