Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
nam thuc » nam thuoc, am thuc, nam thu
doc sach » hoc sach, nuoc sach, dac sac
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
tai cau » tai cao
tai cac » tai cuc
va dan » ca dan, va dao, 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 (doc sach)) ky tang xa hoi. hieu va nam thuc va dan ((tai cau) or (tai cac)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky tang xa hoi. hieu va nam thuc va dan ((tai cau) OR (tai cac)) treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ky tang xa hoi. hieu va nam thuc va dan ((tai cau) or (tai cac)) treo".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ky tang xa hoi. hieu va nam thuc va dan ((tai cau) or (tai cac)) treo*.