Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
thanh dai » thanh hai, thanh dat, thanh oai
te sach » toc sach
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
ty hang » ly hang, ty xang, thi hang
cua tre » cua te, cuu tre, cua triet
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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