Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
thuc va » thuc vat, thuc dan, thuc day
sach sy » sach y, sach ty, sach hay
hieu va » hieu qua
cau tre » cau tren, cau treo, cau tra
long ha » dong ha, cong ha, dong hoa
long xa » song xa, lang xa, dong xa
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va cau » van cau, va cac, va dau

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