Perhaps you should try some spelling variations:
khanh toan » thanh toan, khanh thanh, khanh thuan
cau tren » cu tren, dau tren, ca tren
toan cau » toan cao, toan ban, toan tap
duc van » duc va, duc tan, duc manh
xuc van » luc van, vuc van, xuc ban
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
so hai » son hai, su hai, so ha
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 (so hai)). hieu ve cac ((xuc van) or (duc 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 (so hai)). hieu ve cac ((xuc van) OR (duc van)) khanh toan cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (so hai)). hieu ve cac ((xuc van) or (duc van)) khanh toan cau tren*.