Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
doi nghiem » thi nghiem, doi nghi, hoi nhiem
dat nghe » day nghe, da nghe, dang nghe
sach doi » sach hoi, sach moi, sach dao
tu hanh » du hanh, lu hanh, thuc hanh
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.

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu hanh ((dat nghe) or (van nghe)) d hoc ) or ( thuoc sach doi nghiem ((su hoc) or (tu hoc)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu hanh ((dat nghe) OR (van nghe)) d hoc ) OR ( thuoc sach doi nghiem ((su hoc) OR (tu hoc)) )).
• Adding a wildcard symbol may retrieve word variants: (( tu hanh ((dat nghe) or (van nghe)) d hoc ) or ( thuoc sach doi nghiem ((su hoc) or (tu hoc)) ))*.