Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » thien van, lieu va, hieu ve
te sach » toc sach
hieu va » lieu va, hieu qua
hanh va » hang va, hanh vi
duc van » duc va, duc tan, duc manh
cao duc » dao duc, cao suc, giao duc
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
va cua » va chua, via cua, ca cua
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

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