Perhaps you should try some spelling variations:
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, dieu hien, chieu chien
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
cac tu » cac thu, cach tu, cac du
dan va » doan va, dan ca, ban va
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang x hoi. ((hieu vien) or (hieu hien)) cac tu va ((dan va) or (don vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang x hoi. ((hieu vien) OR (hieu hien)) cac tu va ((dan va) OR (don vi)) cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang x hoi. ((hieu vien) or (hieu hien)) cac tu va ((dan va) or (don vi)) cua tre*.