Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau treo » cau theo, cau tren, cau triet
dang xay » dang van, van xay
lang ha » long ha
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan tai, dan vat, den vai
dan va » doan va, dan ca, ban va
va nam » van nam, ha nam, va nay

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 ((dang xay) or (lang ha)) hoi. hieu va nam thuc va ((dan vai) OR (dan va)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((dang xay) OR (lang ha)) hoi. hieu va nam thuc va ((dan vai) OR (dan va)) cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y ((dang xay) or (lang ha)) hoi. hieu va nam thuc va ((dan vai) OR (dan va)) cau treo".
• Adding a wildcard symbol may retrieve word variants: toc sach y ((dang xay) or (lang ha)) hoi. hieu va nam thuc va ((dan vai) OR (dan va)) cau treo*.