Perhaps you should try some spelling variations:
nham thuc » nhan thuc, nam thuc, nham thu
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hieu ve » hieu va
sang xa » song xa, lang xa, sang ma
sach ty » sach y, sach tu, sach thu
ty sang » ty xang, ty hang, duy sang
thuc va » thuc vat, thuc dan, thuc day
dinh vi » dinh ve, dinh viet, dinh tri
cuu tre » cua tre, cau tren, cau treo

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ty sang xa hoi. ((hieu ve) OR (hieu van)) nham thuc va ((dinh vi) or (chinh tri)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty sang xa hoi. ((hieu ve) OR (hieu van)) nham thuc va ((dinh vi) OR (chinh tri)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty sang xa hoi. ((hieu ve) OR (hieu van)) nham thuc va ((dinh vi) or (chinh tri)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ty sang xa hoi. ((hieu ve) OR (hieu van)) nham thuc va ((dinh vi) or (chinh tri)) cuu tre*.