Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
doanh va » doanh tai, doanh cua, hanh va
thuc van » thuc vat, thuc dan, thuc va
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
duy sang » duy van, duy can, duy anh
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa
y sang » _ sang

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

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