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