Perhaps you should try some spelling variations:
ha nghiem » khao nghiem, thi nghiem, thu nghiem
dang nghe » lang nghe, nang nghe, cong nghe
nghiem du » nghiem dau, nghiem d, nghiem de
dao nghe » day nghe, da nghe, dat nghe
hoach ha » hoach va, hoach xay, hoach hoi
tu sach » thu sach, su sach, te sach
du hoc » tu hoc, duoc hoc
d hoc » ad 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) or (dang nghe)) d hoc ) or ( thu hoach ha nghiem du hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ((dao nghe) OR (dang nghe)) d hoc ) OR ( thu hoach ha nghiem du hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((dao nghe) or (dang nghe)) d hoc ) or ( thu hoach ha nghiem du hoc ))*.