Perhaps you should try some spelling variations:
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, dieu hien, chieu chien
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach y, sach kem
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
cac tu » cac thu, cach tu, cac du
tu van » tu va
vi cua » vai cua, di cua
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: tu ((sach ky) OR (sach ty)) nang x hoi. ((hieu vien) or (hieu hien)) cac tu van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach ty)) nang x hoi. ((hieu vien) OR (hieu hien)) cac tu van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach ty)) nang x hoi. ((hieu vien) or (hieu hien)) cac tu van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach ty)) nang x hoi. ((hieu vien) or (hieu hien)) cac tu van hanh vi cua tre*.