Perhaps you should try some spelling variations:
khanh toan » thanh toan, khanh thanh, khanh thuan
hieu vien » hieu hien, hieu viec, thieu nien
toan cau » toan cao, toan ban, toan tap
vien cac » vien bach, vien dai, vien da
thu sach » tu sach, thuat sach, thuoc sach
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
xuc van » luc van, vuc van, xuc ban
duc van » duc va, duc tan, duc manh
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: thu sach ky nang ((o hoi) or (o hai)). hieu vien cac ((xuc van) or (duc van)) khanh toan cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((o hoi) OR (o hai)). hieu vien cac ((xuc van) OR (duc van)) khanh toan cau tren.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((o hoi) or (o hai)). hieu vien cac ((xuc van) or (duc van)) khanh toan cau tren*.