Perhaps you should try some spelling variations:
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach kem
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
ve ban » te ban, va ban, ve bao
vi cua » vai cua, di cua
ve bac » ve bao, ve cac, he bac
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 ty)) nang x hoi. hieu ((ve bac) or (ve 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 ty)) nang x hoi. hieu ((ve bac) OR (ve ban)) bo va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach ty)) nang x hoi. hieu ((ve bac) or (ve ban)) bo va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach ty)) nang x hoi. hieu ((ve bac) or (ve ban)) bo va hanh vi cua tre*.