Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cau treo » cau theo, cau tren, cau triet
dau tren » dau tien, dat tren, dau tieng
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 (dau 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 (dau 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 (dau tren))*.