Perhaps you should try some spelling variations:
nghiem su » nghiem xu, nghiem ngu, nghiem dau
ha nghiem » khao nghiem, thi nghiem, thu nghiem
hoach ha » hoach va, hoach xay, hoach hoi
tu sach » thu sach, su sach, te sach
sach da » sach dao, sach dat, sach dau
da nghe » day nghe, va nghe, dang nghe
de hoc » te hoc, du hoc, dien hoc
su hoc » tu hoc, du hoc, so hoc
d hoc » du hoc, y hoc, _ 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 (ad 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 ((((d hoc) OR (ad 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 ((((d hoc) OR (ad hoc))) or (de hoc)) ) or ( thu hoach ha nghiem su hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach da nghe ((((d hoc) OR (ad hoc))) or (de hoc)) ) or ( thu hoach ha nghiem su hoc ))*.