Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
nang dai » nang dau, nang tai, lang dai
cua tre » cua te, cuu tre, cua triet
hai cua » thai cua, dai cua, hoi cua
va hanh » van hanh, va thanh, va danh
dai hoi » dai hoc, dai hai, dai moi
hieu ve » hieu va
cac duc » cac du, cao duc, cac dac
su sac » su sach, su cac
su xac » pu xac, su cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sac) or (su xac)) ky nang dai hoi. ((hieu ve) OR (hieu van)) cac duc va hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sac) OR (su xac)) ky nang dai hoi. ((hieu ve) OR (hieu van)) cac duc va hanh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sac) or (su xac)) ky nang dai hoi. ((hieu ve) OR (hieu van)) cac duc va hanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sac) or (su xac)) ky nang dai hoi. ((hieu ve) OR (hieu van)) cac duc va hanh hai cua tre*.