Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
nam thuc » nam thuoc, am thuc, nam thu
hieu va » lieu va, hieu qua
tu cach » tu cac
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
su sach » so sach, vu sach
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: ((tu cach) or (su sach)) ky lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (su sach)) ky lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (su sach)) ky lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (su sach)) ky lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van hanh vi cua tre*.