Perhaps you should try some spelling variations:
ha nghiem » khao nghiem, thi nghiem, thu nghiem
nghiem tu » nghiep tu, nghiem su, nghiem te
toc sach » hoc sach, doc sach, thuoc sach
dao nghe » day nghe, da nghe, nao nghe
dat nghe » day nghe, da nghe, dang nghe
hoach ha » hoach va, hoach xay, hoach hoi
du hoc » duoc hoc
tu hoc » te 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: (( toc sach ((dao nghe) OR (dat nghe)) ((d hoc) or (du hoc)) ) or ( thu hoach ha nghiem tu hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( toc sach ((dao nghe) OR (dat nghe)) ((d hoc) OR (du hoc)) ) OR ( thu hoach ha nghiem tu hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( toc sach ((dao nghe) OR (dat nghe)) ((d hoc) or (du hoc)) ) or ( thu hoach ha nghiem tu hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( toc sach ((dao nghe) OR (dat nghe)) ((d hoc) or (du hoc)) ) or ( thu hoach ha nghiem tu hoc ))*.