Perhaps you should try some spelling variations:
khanh toan » thanh toan, khanh thanh, khanh thuan
van khanh » van thanh, van hanh, van anh
toan cau » toan cao, toan ban, toan tap
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
cac luc » cau luc, coc luc, cac nuoc
luc van » luoc van, luu van, duc van
co hoi » co hoc, co loi
o hoi » o hoc, o hoa
o hai » co hai, so hai, o lai

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 hoi))) or (o hai)). hieu va cac luc van khanh toan cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((((o hoi) OR (co hoi))) OR (o hai)). hieu va cac luc van khanh toan cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((((o hoi) or (co hoi))) or (o hai)). hieu va cac luc van khanh toan cau tren*.