Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
va thanh » gia thanh, ban thanh, va tinh
thanh di » thanh doi, thanh de, thanh do
cau tren » cu tren, dau tren, ca tren
te sach » toc sach
sach ki » sach kinh, sach bai, sach kem
ki nang » ky nang
cac duc » cac du, cao duc, cac dac
cuu tre » cua tre, cau treo
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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 ki nang o hoi. ((hieu van) or (lieu va)) cac duc va thanh di ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ki nang o hoi. ((hieu van) OR (lieu va)) cac duc va thanh di ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ki nang o hoi. ((hieu van) or (lieu va)) cac duc va thanh di ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: te sach ki nang o hoi. ((hieu van) or (lieu va)) cac duc va thanh di ((cuu tre) OR (cau tren))*.