Perhaps you should try some spelling variations:
sach thi » sach thu, sach tai, sach thieu
thi nang » thi cong, ki nang, thi hanh
hieu van » hieu va, thien van, hieu ve
va thanh » gia thanh, ban thanh, va tinh
thanh di » thanh doi, thanh de, thanh do
te sach » toc sach
cac duc » cac du, cao duc, cac dac
cuu tre » cua tre, cau tren, cau treo
di cuu » di cau, di cua, dinh cuu
o hoi » co hoi, o hai, o hoa
o hoc » co hoc, mo hoc, so hoc

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