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 thu
vai cuu » vai cua
cuu tre » cua tre, cau tren, cau treo
hieu ca » hieu cac, hieu cua, hieu va
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
va dan » ca dan, va dau, va dap
va dao » ca dao
ca nam » cua nam, cai nam, ha nam

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