Perhaps you should try some spelling variations:
hanh vai » hanh vi, hanh va, hanh tai
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
trung va » truong va, trang va, trung ha
vai cua » dai cua, hai cua, lai cua
van dau » van dao, phan dau
truc va » thuc va, thuc vat
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet

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 ky) or (sach thu)) nang xa hoi. hieu van dau ((truc va) OR (trung va)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach thu)) nang xa hoi. hieu van dau ((truc va) OR (trung va)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sach thu)) nang xa hoi. hieu van dau ((truc va) OR (trung va)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach thu)) nang xa hoi. hieu van dau ((truc va) OR (trung va)) hanh vai cua tre*.