Perhaps you should try some spelling variations:
chat thuc » thuat thuc, nhan thuc, chat thai
toc sach » hoc sach, doc sach, thuoc sach
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
van hoi » van hoa, van hoc, van hoe
y tang » ky tang, 7 tang, 5 tang
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di 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 ((y tang) or (6 tang)) van hoi. ((hieu ve) OR (hieu va)) chat thuc va dan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((y tang) OR (6 tang)) van hoi. ((hieu ve) OR (hieu va)) chat thuc va dan vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((y tang) or (6 tang)) van hoi. ((hieu ve) OR (hieu va)) chat thuc va dan vi cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((y tang) or (6 tang)) van hoi. ((hieu ve) OR (hieu va)) chat thuc va dan vi cua tre*.