Perhaps you should try some spelling variations:
nghien su » nghiem su, nghiep sua, nghiep vu
sach dao » lanh dao
dao nghe » day nghe, da nghe, dat nghe
hoach va » hoach xay, hanh va, doanh va
tu sach » thu sach, su sach, te sach
nghe d » nghe di, nghe _, nghe 新
d hoc » du hoc, ad hoc, de hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach dao nghe d hoc ) or ( thu hoach va ((nghien su) OR (nghien cuu)) hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dao nghe d hoc ) OR ( thu hoach va ((nghien su) OR (nghien cuu)) hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach dao nghe d hoc ) or ( thu hoach va ((nghien su) OR (nghien cuu)) hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach dao nghe d hoc ) or ( thu hoach va ((nghien su) OR (nghien cuu)) hoc ))*.