Perhaps you should try some spelling variations:
cau triet » cau trieu, su triet, cua triet
cau treo » cau theo, cau tren, cau trieu
nam thuc » nam thuoc, am thuc, nam thu
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
tang ma » mang may, tang van
sach ky » sac ky, sach y, sach ty
tang xa » trang xa, lang xa, tang ha
thuc va » thuc vat, thuc dan, thuc day
van tai » von tai, van tuan

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