Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
dan dinh » dang dinh, doan dinh, van dinh
thuc dan » thuc hanh, hoc dan, thuc vat
can thuc » dan thuc, van thuc, cay thuc
so sach » so sanh, bo sach, co sach
dinh vi » dinh ve, dinh viet, dinh tri
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
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: so sach y ((nang xa) or (nang ma)) hoi. ((hieu van) OR (hieu va)) can thuc dan dinh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang xa) OR (nang ma)) hoi. ((hieu van) OR (hieu va)) can thuc dan dinh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y ((nang xa) or (nang ma)) hoi. ((hieu van) OR (hieu va)) can thuc dan dinh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang xa) or (nang ma)) hoi. ((hieu van) OR (hieu va)) can thuc dan dinh vi cua tre*.