Perhaps you should try some spelling variations:
va nghiem » van nghiem, va nghien, va nghiep
thu doanh » thu oanh, tri doanh, thu hoach
sach dao » lanh dao
dao nghe » day nghe, da nghe, dat nghe
doanh va » doan va, doanh tai, doanh cua
tu sach » thu sach, su sach, te sach
su hoc » du hoc, so hoc, su ho
tu hoc » te hoc
d hoc » du hoc, de hoc, y 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 (ad hoc)) ) or ( thu doanh va nghiem ((su hoc) or (tu hoc)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dao nghe ((d hoc) OR (ad hoc)) ) OR ( thu doanh va nghiem ((su hoc) OR (tu hoc)) )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach dao nghe ((d hoc) or (ad hoc)) ) or ( thu doanh va nghiem ((su hoc) or (tu hoc)) ))*.