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
doan vi » doan va, don vi, doan thi
cac thu » cach thuc, cac thoi
cua tre » cua te, cuu tre, cua triet
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
cac tu » cach tu, cac du, tac tu
dan vi » don vi, dan va, gan vi

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 lang xa hoi. hieu vien ((cac tu) OR (cac thu)) va ((dan vi) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang xa hoi. hieu vien ((cac tu) OR (cac thu)) va ((dan vi) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang xa hoi. hieu vien ((cac tu) OR (cac thu)) va ((dan vi) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang xa hoi. hieu vien ((cac tu) OR (cac thu)) va ((dan vi) or (doan vi)) cua tre*.