Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
cau treo » cau theo, cau triet, cau trieu
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
doc sach » hoc sach, nuoc sach, dac sac
cau tren » cu tren, dau tren, ca tren
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
thuc va » thuc vat, thuc dan, thuc day
va tao » va bao, va cao, va tac

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