Perhaps you should try some spelling variations:
thanh doi » thanh loi, thanh moi, thanh do
dan thanh » dang thanh, danh thanh, ban thanh
cam thuc » am thuc, nam thuc, cam thu
hieu van » thien van, lieu va, hieu ve
thuc dan » thuc hanh, hoc dan, thuc vat
so sach » bo sach, co sach, hoc sach
doi cua » dai cua, hoi cua
so sanh » do sanh
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
y lang » o lang, _ lang, tay lang
cua tu » cua tuc, cua su, cua cu

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) or (so sanh)) y lang xa hoi. ((hieu van) OR (hieu va)) cam thuc dan thanh doi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (so sanh)) y lang xa hoi. ((hieu van) OR (hieu va)) cam thuc dan thanh doi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) or (so sanh)) y lang xa hoi. ((hieu van) OR (hieu va)) cam thuc dan thanh doi cua tu".
• Adding a wildcard symbol may retrieve word variants: ((so sach) or (so sanh)) y lang xa hoi. ((hieu van) OR (hieu va)) cam thuc dan thanh doi cua tu*.