Perhaps you should try some spelling variations:
thi hang » thi hanh, thi nang, thi hong
va thanh » ban thanh, va tinh, le thanh
sach thi » sach thu, sach tai, sach thieu
te sach » toc sach
cac tuc » cac toc, cac tu, cac tac
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
do cua » doi cua, co cua, de cua
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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