Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nang cai » nang cao, nang cap, nang can
hanh vai » hanh vi, hanh va, hanh tai
nang tai » hang tai, tang tai, sang tai
so sach » so sanh, bo sach, co sach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cam tuc » cam xuc, cam tu, nam thuc
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang cai) or (nang tai)) hoi. ((hieu ve) or (hieu van)) cam tuc va hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang cai) OR (nang tai)) hoi. ((hieu ve) OR (hieu van)) cam tuc va hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang cai) or (nang tai)) hoi. ((hieu ve) or (hieu van)) cam tuc va hanh vai cua tre*.