Perhaps you should try some spelling variations:
xay nghiem » xet nghiem, day nghiep, van nghiem
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 » 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 ((dao nghe) OR (dat nghe)) d hoc ) or ( thu hoach xay nghiem ((su hoc) or (so hoc)) ))~.
• 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 xay nghiem ((su hoc) OR (so 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 xay nghiem ((su hoc) or (so hoc)) ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((dao nghe) OR (dat nghe)) d hoc ) or ( thu hoach xay nghiem ((su hoc) or (so hoc)) ))*.