Perhaps you should try some spelling variations:
sang dai » sang tai, lang dai, sang mai
hanh vai » hanh va, hanh tai, hanh van
ky sang » ky nang, ky dang, ky tang
dai hoi » dai hoc, dai hai, dai moi
hieu ve » hieu van
hieu va » lieu va, hieu qua
cao duc » dao duc, cao suc, giao duc
cuu tre » cua tre, cau tren, cau treo

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

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