Perhaps you should try some spelling variations:
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
sach tu » sach thu, cach tu, sach ty
va ban » van ban, va bai, va bao
vi cua » vai cua, di cua
ve bac » ve bao, ve cac, ve ban
x hoi » xa hoi, o hoi, x ho
bo va » bao va, do va, so va

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 tu)) nang x hoi. hieu ((ve bac) or (va ban)) bo va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach tu)) nang x hoi. hieu ((ve bac) OR (va ban)) bo va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach tu)) nang x hoi. hieu ((ve bac) or (va ban)) bo va hanh vi cua tre*.