Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
ban thanh » ban hanh, ban hang
hieu cua » hieu qua, dieu cua, bieu cua
tai cua » thai cua, tai cuc, tri cua
cac duc » cao duc, cac dac, cac nuoc
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ty ((tang ma) or (lang xa)) hoi. hieu cua ((cac duc) OR (cac du)) ban thanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((tang ma) OR (lang xa)) hoi. hieu cua ((cac duc) OR (cac du)) ban thanh tai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((tang ma) or (lang xa)) hoi. hieu cua ((cac duc) OR (cac du)) ban thanh tai cua tre*".