Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh tai » thanh hai, thanh toan, doanh tai
tu sach » thu sach, su sach, te sach
ty nang » ty xang, ty hang, ly nang
cua tre » cuu tre, cua triet, dua tren
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
duc ban » duc tan, duc van, dua ban
ve cac » va cac, vien cac
cua te » cua tu
o hoi » co hoi, o hoc, o hai

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) OR (ky nang)) o hoi. 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) OR (ky nang)) o hoi. 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) OR (ky nang)) o hoi. hieu ve cac duc ban thanh tai ((cua tre) or (cua te))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty nang) OR (ky nang)) o hoi. hieu ve cac duc ban thanh tai ((cua tre) or (cua te))*.