Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien bac » vien bach, vien cac, mien bac
danh vai » danh sai, danh va, doanh van
tu sach » thu sach, te sach, tu cach
su sach » so sach, vu sach
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
cao va » cao van, tao va
co va » co ma, do va, so va

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) or (su sach)) ky nang x ho. hieu vien bac ((cao va) OR (co va)) danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky nang x ho. hieu vien bac ((cao va) OR (co va)) danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky nang x ho. hieu vien bac ((cao va) OR (co va)) danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky nang x ho. hieu vien bac ((cao va) OR (co va)) danh vai cua tre*.