Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
cac dac » cac dan, cac dai, cac bac
dan thi » dang thi, tran thi, dinh thi
thi cua » thai cua, thi cuc, tri cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
x hoi » xa hoi, o hoi, 5 hoi

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 y nang ((x hoi) or (x ho)). hieu va ((cac tuc) or (cac dac)) va dan thi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((x hoi) OR (x ho)). hieu va ((cac tuc) OR (cac dac)) va dan thi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((x hoi) or (x ho)). hieu va ((cac tuc) or (cac dac)) va dan thi cua tre*.