Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nam thuc » nam thuoc, am thuc, nam tu
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, tang ha
cuu tre » cua tre, cau tren, cau treo
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va cuu » va cau, va chu, va huu

You may be able to get more results by adjusting your search query.

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