Perhaps you should try some spelling variations:
present challenges » current challenges, assessment challenges
wang yang » wang yan, wang liang, wang yanling
min hong » amin hong, min hyoung, min jeong
tin hong » tan hong, kia hong, thi hong
yang xi » yang di, yang yi, yang jui
ya 2 » a 2, na 2, 4a 2
ca 2 » a 2, c 2, ch 2

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 ((ya 2) or (ca 2)) present challenges ((min hong) OR (tin hong)) hai ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((wang yang) OR (yang xi))ng ((ya 2) OR (ca 2)) present challenges ((min hong) OR (tin hong)) hai ;.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((wang yang) or (yang xi))ng ((ya 2) or (ca 2)) present challenges ((min hong) OR (tin hong)) hai ;".
• Adding a wildcard symbol may retrieve word variants: ((wang yang) or (yang xi))ng ((ya 2) or (ca 2)) present challenges ((min hong) OR (tin hong)) hai ;*.