Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
van thanh » ban thanh, van tuan
cau tren » cu tren, dau tren, ca tren
thai cau » thai cao, toan cau, thai van
van hanh » ban hanh, van anh, van ban
vien cac » vien bach, vien dai, vien da
sach ky » sac ky, sach y, sach ty
cac xuc » cam xuc, cac nuoc, chat xuc
tu sach » thu sach, su sach, te sach
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 ky nang ((o hoi) or (o hai)). hieu vien cac xuc ((van hanh) or (van thanh)) thai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hai)). hieu vien cac xuc ((van hanh) OR (van thanh)) thai cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o hai)). hieu vien cac xuc ((van hanh) or (van thanh)) thai cau tren*.