Perhaps you should try some spelling variations:
thu nghiem » thuc nghiem, thi nghiem
hoach thu » hoach thay, doanh thu, hoach su
dao nghe » day nghe, da nghe, nao nghe
dat nghe » day nghe, da nghe, dang nghe
tu sach » thu sach, su sach, te sach
su hoc » du hoc, so hoc, su ho
tu hoc » te hoc
d hoc » du hoc, ad hoc, de hoc

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ((dao nghe) OR (dat nghe)) d hoc ) OR ( thu hoach thu nghiem ((su hoc) OR (tu hoc)) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ((dao nghe) OR (dat nghe)) d hoc ) or ( thu hoach thu nghiem ((su hoc) or (tu hoc)) ))~".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((dao nghe) OR (dat nghe)) d hoc ) or ( thu hoach thu nghiem ((su hoc) or (tu hoc)) ))*.