Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
truc va » thuc va, thuc vat, trung va
sach ky » sac ky, sach y, sach ty
van cam » van nam, van lam, van cau
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, tuc xa, duc va
ma hoi » xa hoi, ma hoa, me 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 ky dang ((ma hoi) or (mai hoi)). hieu van cam ((tuc va) OR (truc va)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((ma hoi) OR (mai hoi)). hieu van cam ((tuc va) OR (truc va)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((ma hoi) or (mai hoi)). hieu van cam ((tuc va) OR (truc va)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((ma hoi) or (mai hoi)). hieu van cam ((tuc va) OR (truc va)) hanh vai cua tre*.