Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, ban thanh, va tinh
thanh di » thanh doi, thanh de, thanh do
tu sach » thu sach, su sach, te sach
cao hoi » co hoi, cao hoc, tao hoi
hieu ve » hieu va
cam duc » cam xuc, cao duc, pham duc
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
di cua » dai cua, doi cua, de 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 ((cao hoi) or (cau hoi)). ((hieu ve) OR (hieu van)) cam duc va thanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((cao hoi) OR (cau hoi)). ((hieu ve) OR (hieu van)) cam duc va thanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((cao hoi) or (cau hoi)). ((hieu ve) OR (hieu van)) cam duc va thanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((cao hoi) or (cau hoi)). ((hieu ve) OR (hieu van)) cam duc va thanh di cua tre*.