Perhaps you should try some spelling variations:
hai thuc » thai thuc, dai thuc, ha thuc
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
cua tre » cua te, cua triet, dua tren
thuc va » thuc vat, thuc dan, thuc day
van hai » van ha, van chat, van hanh
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
cuu tre » cau tren, cau treo
va dao » ca dao
dao vi » dao voi, dao ve, dao va

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

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