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

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