Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau treo » cau tren, cau triet, cau trieu
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cau theo » cau thi, cau tao
long ha » dong ha, cong ha, dong hoa
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
va dan » ca dan, va dao, va dau

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 ((lang xa) or (long ha)) hoi. hieu van nam thuc va dan vai ((cau treo) or (cau theo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((lang xa) OR (long ha)) hoi. hieu van nam thuc va dan vai ((cau treo) OR (cau theo)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((lang xa) or (long ha)) hoi. hieu van nam thuc va dan vai ((cau treo) or (cau theo))*.