Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
nam thuc » nam thuoc, am thuc, nam tu
cau treo » cau theo, cau tren, cau triet
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu ha » hieu hoa, hieu va, hieu ca
dao vai » dao van, dao va, dao bai
vai cau » va cau, van cau, vai cac
va dao » ca dao

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