Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
nang xa » nang x, lang xa, nang ma
hieu va » hieu qua
sach ky » sac ky, sach y, sach ty
vai cuu » vai cua
cuu tre » cua tre, cau tren, cau treo
va dan » ca dan, va dau, va dap
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 ky nang xa hoi. ((hieu va) or (lieu va)) 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 ky nang xa hoi. ((hieu va) OR (lieu va)) nam thuc ((va dan) OR (va dao)) vai cuu tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang xa hoi. ((hieu va) or (lieu va)) nam thuc ((va dan) or (va dao)) vai cuu tre*.