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 va, thuc hanh
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
ty nang » ty xang, ty hang, ly nang
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 ((ty nang) OR (ky nang)) xa hoi. hieu vien day ((thuc van) or (thuc dan)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty nang) OR (ky nang)) xa hoi. hieu vien day ((thuc van) OR (thuc dan)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty nang) OR (ky nang)) xa hoi. hieu vien day ((thuc van) or (thuc dan)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty nang) OR (ky nang)) xa hoi. hieu vien day ((thuc van) or (thuc dan)) hanh vi cua tre*.