Perhaps you should try some spelling variations:
sach tranh » canh tranh
tranh nghe » trinh nghe, anh nghe, hanh nghe
tai nghiem » trai nghiem, thi nghiem, trac nghiem
nghiem van » nghiem va, nghiem ban, nghiep van
bach tai » bach mai, bac tai, sach tai
tu sach » thu sach, su sach, te sach
nghe de » nghe det, nghe di, nghe te
van hoc » van hoa
de hoc » te hoc, du hoc, dien 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 tranh nghe de hoc ) or ( vu bach tai nghiem van hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tranh nghe de hoc ) OR ( vu bach tai nghiem van hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tranh nghe de hoc ) or ( vu bach tai nghiem van hoc ))*.