Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cam tuc » cam xuc, cam tu, dam thuc
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 ((cam tuc) OR (nam thuc)) va 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 ((cam tuc) OR (nam thuc)) va hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky tang ma hoi. hieu van ((cam tuc) OR (nam thuc)) va hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang ma hoi. hieu van ((cam tuc) OR (nam thuc)) va hanh vai cua tre*.