Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cau treo » cau theo, cau tren, cau triet
lang xa » lang ha, lang van
long ha » dong ha, cong ha, dong hoa
vat dan » va dan, van dan, vat ran
dan vat » dang vat, van vat, dan va
vat cau » dat cau, va cau, van cau

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