Perhaps you should try some spelling variations:
challenges belonging » challenges emerging, challenges branding, challenges changing
gap recent » gaap recent, a recent, amp recent
gas recent » cas recents, gaap recent, a recent
among di » among hiv, among idp, among _
nan yan » nan ya, wang yan, qian yan
yang xi » yang di, yang yi, yang jui

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((nan yan) or (yang xi))ng ra ((gas recent) OR (gap recent)) challenges belonging among di ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((nan yan) OR (yang xi))ng ra ((gas recent) OR (gap recent)) challenges belonging among di ;*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((nan yan) or (yang xi))ng ra ((gas recent) OR (gap recent)) challenges belonging among di ;*".