Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
dinh thi » dinh tri
van dinh » van minh, van dich, va dinh
tu sach » thu sach, su sach, te sach
thi cua » thai cua, thi cuc, tri cua
duc van » duc va, duc tan, duc manh
cao duc » dao duc, cao suc, giao duc
hieu ve » hieu va
cua te » cua tu
y nang » ky nang, ly nang, v nang
o lai » o lao
o hai » co hai, so hai, _ hai

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