Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
dang xa » dang xay, lang xa, dang ha
hieu va » hieu qua
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va cua » va chua, via cua, ca cua

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 dang xa hoi. ((hieu va) OR (lieu va)) nam thuc va dan va cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky dang xa hoi. ((hieu va) OR (lieu va)) nam thuc va dan va cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang xa hoi. ((hieu va) OR (lieu va)) nam thuc va dan va cua tre*.