Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
tay lang » tai lang, tay tang, tay quang
hieu van » hieu va, thien van, lieu va
so sach » bo sach, co sach, hoc sach
so sanh » do sanh
thuc va » thuc vat, thuc dan, thuc day
de cua » le cua, te cua, dieu cua
dan de » dan den, dang de, van de
va dan » ca dan, va dao, va dau
cua te » cua tu
ha hoi » hoa hoi, xa hoi, va hoi

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