Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
long ha » dong ha, cong ha, dong hoa
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
cuu tre » cua tre, cau treo
va dan » ca dan, va dao, va dau
va nam » van nam, ha nam, va nay

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 ((lang ha) OR (long ha)) hoi. hieu va nam thuc va dan vai ((cuu tre) OR (cau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky ((lang ha) OR (long ha)) hoi. hieu va nam thuc va dan vai ((cuu tre) or (cau tren))~".
• Adding a wildcard symbol may retrieve word variants: doc sach ky ((lang ha) OR (long ha)) hoi. hieu va nam thuc va dan vai ((cuu tre) or (cau tren))*.