Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
bach tu » bach thu, cach tu, bac tu
cua tre » cua te, cuu tre, cua triet
ca dan » cac dan, ca dao
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di cua
tu ca » tu cac, tu cua, tu can

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 ((x ho) or (xa hoi)). hieu vien bach tu ca dan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x ho) OR (xa hoi)). hieu vien bach tu ca dan vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((x ho) or (xa hoi)). hieu vien bach tu ca dan vi cua tre*.