Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
cao duc » dao duc, cao suc, giao duc
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
vi cua » vai cua, di cua

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 y ((nang xa) OR (lang xa)) hoi. ((hieu ve) or (hieu va)) cao duc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (lang xa)) hoi. ((hieu ve) OR (hieu va)) cao duc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) OR (lang xa)) hoi. ((hieu ve) or (hieu va)) cao duc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang xa) OR (lang xa)) hoi. ((hieu ve) or (hieu va)) cao duc van hanh vi cua tre*.