Perhaps you should try some spelling variations:
thu nghiem » thuc nghiem, thi nghiem
hoach thu » hoach thay, doanh thu, hoach su
nghiem du » nghiem dau, nghiem d, nghiem de
sach dau » sach dao, sach dat, sach mau
dau nghe » day nghe, da nghe, dat nghe
tu sach » thu sach, su sach, te sach
de hoc » te hoc, dien hoc
du hoc » tu hoc, duoc hoc
d hoc » ad hoc, y hoc, _ 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 dau nghe ((d hoc) or (de hoc)) ) or ( thu hoach thu nghiem du hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dau nghe ((d hoc) OR (de hoc)) ) OR ( thu hoach thu nghiem du hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach dau nghe ((d hoc) or (de hoc)) ) or ( thu hoach thu nghiem du hoc ))*.