Perhaps you should try some spelling variations:
van doanh » toan doanh, van dong, van thanh
sach thue » sach thu, sach thieu, sach tham
nam thuc » nam thuoc, am thuc, nam thu
doanh va » doan va, doanh tai, doanh cua
thuc van » thuc vat, thuc dan, thuc va
hieu van » thien van, lieu va, hieu ve
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
va cua » va chua, via cua, ca cua

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) or (sach thue)) lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van doanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach ty) OR (sach thue)) lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van doanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc ((sach ty) or (sach thue)) lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van doanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: toc ((sach ty) or (sach thue)) lang xa hoi. ((hieu van) OR (hieu va)) nam thuc van doanh va cua tre*.