Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
sach thi » sach thu, sach tai, sach thieu
thi nang » thi cong, ki nang, thi hanh
thanh di » thanh doi, thanh de, thanh do
hieu van » hieu va, thien van, hieu ve
va thanh » gia thanh, ban thanh, va tinh
cuu tre » cua tre, cau treo
te sach » toc sach
cac luc » cau luc, coc luc, cac nuoc
luc va » duc va, tuc va, loc va
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 thi nang o hoi. ((hieu van) or (lieu va)) cac luc va thanh di ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thi nang o hoi. ((hieu van) OR (lieu va)) cac luc va thanh di ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach thi nang o hoi. ((hieu van) or (lieu va)) cac luc va thanh di ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: te sach thi nang o hoi. ((hieu van) or (lieu va)) cac luc va thanh di ((cuu tre) OR (cau tren))*.