Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
thuc day » thuc dan, thuc vat
trung va » truong va, trang va, trung ha
tu sach » thu sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
van cau » van dau, van hau, van chat
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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) or (su sach)) ky tang ma hoi. hieu van cau ((trung va) or (thuc day)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky tang ma hoi. hieu van cau ((trung va) OR (thuc day)) hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang ma hoi. hieu van cau ((trung va) or (thuc day)) hanh vai cua tre*.