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