Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien day » vien dai, vien da, vien xay
thuc van » thuc vat, thuc dan, thuc hanh
su sach » vu sach
so sach » so sanh, bo sach, co sach
xang xa » lang xa, mang xa, ang xa
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
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 (so sach)) ty xang xa hoi. hieu vien day ((thuc van) OR (thuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ty xang xa hoi. hieu vien day ((thuc van) OR (thuc va)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) ty xang xa hoi. hieu vien day ((thuc van) OR (thuc va)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ty xang xa hoi. hieu vien day ((thuc van) OR (thuc va)) hanh vi cua tre*.