Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
ban thanh » ban hanh, ban hang
tu sach » thu sach, su sach, te sach
cua tre » cuu tre, cua triet, dua tren
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
ve cac » va cac, vien cac
cua te » cua tu
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: tu sach ty nang ((o hoi) OR (o hai)). hieu ve cac duc ban thanh tai ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((o hoi) OR (o hai)). hieu ve cac duc ban thanh tai ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((o hoi) OR (o hai)). hieu ve cac duc ban thanh tai ((cua tre) or (cua te))".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((o hoi) OR (o hai)). hieu ve cac duc ban thanh tai ((cua tre) or (cua te))*.