Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
hoa hoi » khoa hoi, hoa hoc, hoa doi
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
hieu va » hieu qua
ky dang » ky nang, ky danh
chu tre » cho tre, chu tri, cuu tre
ha hoi » ha noi, xa hoi, va hoi
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va chu » va che, va cau, va chi

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