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
hieu va » hieu qua
cuu tre » cua tre, cau tren, cau treo
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
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.

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