Perhaps you should try some spelling variations:
khanh thai » nhanh thai, khanh thanh, khanh thuan
van khanh » van thanh, van hanh, van anh
cau tren » cu tren, dau tren, ca tren
thai cau » thai cao, toan cau, thai van
cac luc » coc luc, cac nuoc, cac cuoc
cau luc » cau truc, cau phuc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
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 ky nang ((o hoi) or (o hai)). hieu ve ((cac luc) OR (cau luc)) van khanh thai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hai)). hieu ve ((cac luc) OR (cau luc)) van khanh thai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (o hai)). hieu ve ((cac luc) OR (cau luc)) van khanh thai cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o hai)). hieu ve ((cac luc) OR (cau luc)) van khanh thai cau tren*.