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 nuoc » cap nuoc, hoc nuoc, dat nuoc
cac luc » cau luc, coc luc, cac cuoc
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
y nang » ky nang, ly nang, v nang
o hai » co hai, so hai, o lai
o hoa » do hoa, so hoa, o ha

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 y nang ((o hoa) or (o hai)). hieu ve ((cac luc) OR (cac nuoc)) van khanh thai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((o hoa) OR (o hai)). hieu ve ((cac luc) OR (cac nuoc)) van khanh thai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((o hoa) or (o hai)). hieu ve ((cac luc) OR (cac nuoc)) van khanh thai cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((o hoa) or (o hai)). hieu ve ((cac luc) OR (cac nuoc)) van khanh thai cau tren*.