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
hieu van » hieu va, thien van, lieu va
thai cau » thai cao, toan cau, thai van
luc van » luoc van, luu van, duc van
cac luc » cau luc, coc luc, cac nuoc
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va
ty nang » ky nang, ty xang, ty hang
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) OR (hieu van)) cac luc van khanh thai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((o hoi) OR (o hai)). ((hieu ve) OR (hieu van)) cac luc van khanh thai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((o hoi) or (o hai)). ((hieu ve) OR (hieu van)) cac luc van khanh thai cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((o hoi) or (o hai)). ((hieu ve) OR (hieu van)) cac luc van khanh thai cau tren*.