Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
nam thuc » nam thuoc, am thuc, nam thu
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
vai cau » van cau, vai cac, lai chau
va dan » ca dan, va dao, va dau
va cau » van cau, va cac, va dau
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) or (thuoc sach)) ky tang xa hoi. hieu va nam thuc va dan ((vai cau) OR (va cau)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thuoc sach)) ky tang xa hoi. hieu va nam thuc va dan ((vai cau) OR (va cau)) treo*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (thuoc sach)) ky tang xa hoi. hieu va nam thuc va dan ((vai cau) OR (va cau)) treo*".