Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thuc day » thuc dan, thuc vat
su sach » so sach, vu sach
dinh vi » dinh ve, dinh viet, dinh tri
thuc va » thuc vat, thuc dan
van cac » van hac, van cau, van bac
so sanh » do sanh
cao hoi » cau hoi, co hoi, cao hoc
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sanh)) y nang cao hoi. hieu van cac ((thuc va) OR (thuc day)) dinh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sanh)) y nang cao hoi. hieu van cac ((thuc va) OR (thuc day)) dinh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sanh)) y nang cao hoi. hieu van cac ((thuc va) OR (thuc day)) dinh vi cua tre*.