Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien dai » hien dai
hanh tai » thanh tai, hang tai, han tai
so sach » so sanh, bo sach, co sach
luc van » luoc van, luu van, duc van
cuc tre » duc tre, cua tre, cuu tre
y nang » ky nang, ly nang, v nang
o hai » co hai, so hai, _ hai
o lai » o lao

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach y nang ((o hai) OR (o lai)). hieu vien dai ((luc van) or (duc tan)) hanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang ((o hai) OR (o lai)). hieu vien dai ((luc van) OR (duc tan)) hanh tai cuc tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y nang ((o hai) OR (o lai)). hieu vien dai ((luc van) or (duc tan)) hanh tai cuc tre".
• Adding a wildcard symbol may retrieve word variants: so sach y nang ((o hai) OR (o lai)). hieu vien dai ((luc van) or (duc tan)) hanh tai cuc tre*.