Perhaps you should try some spelling variations:
nghiep va » nghiep vu
dien hoc » dien hoa, khien hoc, tin hoc
hoach va » hoach xay, doanh va, hoa 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
hanh va » hang va, hanh vi
va hoc » van hoc
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 (dien hoc)) ) or ( thu ((hoach va) or (hanh va)) nghiep va hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach da nghe ((d hoc) OR (dien hoc)) ) OR ( thu ((hoach va) OR (hanh va)) nghiep va hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach da nghe ((d hoc) or (dien hoc)) ) or ( thu ((hoach va) or (hanh va)) nghiep va hoc ))*.