Perhaps you should try some spelling variations:
ha nghiem » khao nghiem, thi nghiem, thu nghiem
sach dat » sach dao, sach danh, sach bai
dat nghe » day nghe, da nghe, dang nghe
hoach ha » hoach va, hoach xay, hoach hoi
tu sach » thu sach, su sach, te sach
nghe de » nghe det, nghe di, nghe te
de hoc » te hoc, du hoc, dien hoc
su hoc » tu hoc, du hoc, su ho
so hoc » co hoc, so hoa, o hoc
mo hoc » mon hoc, co 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 dat nghe de hoc ) or ( thu hoach ha nghiem ((su hoc) or (((so hoc) OR (mo hoc)))) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dat nghe de hoc ) OR ( thu hoach ha nghiem ((su hoc) OR (((so hoc) OR (mo hoc)))) ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach dat nghe de hoc ) or ( thu hoach ha nghiem ((su hoc) or (((so hoc) OR (mo hoc)))) ))*".