Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
ky long » ky cong, sy long, ky trong
long xa » song xa, long ha, lang xa
hieu va » hieu qua
thuc va » thuc vat, thuc dan, thuc day
dan va » doan va, ban va, han va

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