Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nha thuoc, cay thuoc
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
va dan » ca dan, va dao, va dau
va cau » van cau, va dau, va cao

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