Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
thuc va » thuc vat, thuc dan, thuc day
truc va » thuc vat, trung va
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
te sach » toc sach
cua tre » cua te, cuu tre, cua triet
va cau » van cau, va cac, va dau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) or (te sach)) ky tang xa hoi. hieu va cau ((truc va) OR (thuc va)) hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (te sach)) ky tang xa hoi. hieu va cau ((truc va) OR (thuc va)) hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (te sach)) ky tang xa hoi. hieu va cau ((truc va) OR (thuc va)) hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (te sach)) ky tang xa hoi. hieu va cau ((truc va) OR (thuc va)) hanh dai cua tre*.