Perhaps you should try some spelling variations:
hanh vai » hanh vi, hanh va, hanh tai
van hanh » van thanh, ban hanh, van anh
dang xay » dang van, van xay
so sanh » do sanh
hieu va » lieu va, hieu qua
vai cua » dai cua, hai cua, lai cua
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu van
sanh ky » hanh ky, sang ky, nganh ky
lang xa » lang ha, lang van
cua tre » cua te, cuu tre, cua triet

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

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