Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
van hanh » ban hanh, van anh, van ban
thai cau » thai cao, toan cau, thai van
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
co hai » co dai, co hoi, o hai
va coc » va cuoc, va cac, va hoc
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 ky nang ((o hoi) or (co hai)). hieu va coc luc ((van hanh) or (van thanh)) thai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (co hai)). hieu va coc luc ((van hanh) OR (van thanh)) thai cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (co hai)). hieu va coc luc ((van hanh) or (van thanh)) thai cau tren*.