Perhaps you should try some spelling variations:
related challenges » regulatory challenges
challenges during » challenges facing, changes during, challenges regarding
during zhong » funing zhong, during h1n1
3 related » 2 related
zhong zhi » zhang zhi, hong ghi, zhong tai
yang xi » yang di, yang yi, yang jui
ngo a » ngos a, neo a, ngo _
ngo 1 » nao 1, ngo _
wang » wing, wan, lang

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 yan) OR (yang xi))((ngo a) OR (ngo 1)) 3 related challenges during zhong zhi ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((wang yan) or (yang xi))((ngo a) OR (ngo 1)) 3 related challenges during zhong zhi ;~".
• Adding a wildcard symbol may retrieve word variants: ((wang yan) or (yang xi))((ngo a) OR (ngo 1)) 3 related challenges during zhong zhi ;*.