Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
cac luc » cau luc, coc luc, cac nuoc
tai cua » thai cua, tai cuc, tri cua
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
dai hoi » dai hoc, dai hai, dai moi
ve cac » va cac, vien cac

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 ((cau hoi) or (dai hoi)). hieu ve cac luc ((va hanh) OR (van hanh)) tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang ((cau hoi) OR (dai hoi)). hieu ve cac luc ((va hanh) OR (van hanh)) tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang ((cau hoi) or (dai hoi)). hieu ve cac luc ((va hanh) OR (van hanh)) tai cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang ((cau hoi) or (dai hoi)). hieu ve cac luc ((va hanh) OR (van hanh)) tai cua tre*.