Perhaps you should try some spelling variations:
va nghiem » van nghiem, va nghien, va nghiep
hoach va » hoach xay, hanh va, doanh va
tu sach » thu sach, su sach, te sach
sach da » sach dao, sach dat, sach dau
da nghe » day nghe, va nghe, dang nghe
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 da nghe d hoc ) or ( thu hoach va nghiem ngu hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach da nghe d hoc ) OR ( thu hoach va nghiem ngu hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach da nghe d hoc ) or ( thu hoach va nghiem ngu hoc ))*.