Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien dai » hien dai
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa
ty ang » ty hang, ty anh
vi cua » vai cua, di cua
ac va » tac va, bac va, mac va

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 ((ty ang) OR (ty xang)) xa hoi. hieu vien dai ((ac va) or (tuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty ang) OR (ty xang)) xa hoi. hieu vien dai ((ac va) OR (tuc va)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty ang) OR (ty xang)) xa hoi. hieu vien dai ((ac va) or (tuc va)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty ang) OR (ty xang)) xa hoi. hieu vien dai ((ac va) or (tuc va)) hanh vi cua tre*.