Perhaps you should try some spelling variations:
ha nghiem » khao nghiem, thi nghiem, thu nghiem
nghiem su » nghiem xu, nghiem ngu, nghiem dau
hoach ha » hoach va, hoach xay, hoach hoi
tu sach » thu sach, su sach, te sach
da nghe » day nghe, dang nghe, van nghe
va nghe » van nghe, ve nghe, va nghi
de hoc » te hoc, du hoc, dien hoc
su hoc » tu hoc, du hoc, so hoc
d hoc » du hoc, ad 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 ((da nghe) OR (va nghe)) ((d hoc) or (de hoc)) ) or ( thu hoach ha nghiem su hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ((da nghe) OR (va nghe)) ((d hoc) OR (de hoc)) ) OR ( thu hoach ha nghiem su hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ((da nghe) OR (va nghe)) ((d hoc) or (de hoc)) ) or ( thu hoach ha nghiem su hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((da nghe) OR (va nghe)) ((d hoc) or (de hoc)) ) or ( thu hoach ha nghiem su hoc ))*.