Perhaps you should try some spelling variations:
trach nhiem » trac nghiem
khanh trach » khanh tra
thi nghiem » thuc nghiem
sach thi » sach thu, sach tai, sach thieu
tu khanh » vu khanh, tu hanh, tu thanh
nhiem de » nghiem de, nhiem ve, nhiet de
te sach » toc sach
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: (( te sach thi nghiem _ hoc ) or ( tu khanh trach nhiem de hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach thi nghiem _ hoc ) OR ( tu khanh trach nhiem de hoc )).
• Adding a wildcard symbol may retrieve word variants: (( te sach thi nghiem _ hoc ) or ( tu khanh trach nhiem de hoc ))*.