Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
hieu van » hieu va, thien van, lieu va
tai cua » thai cua, tai cuc, tri cua
thuc va » thuc vat, thuc dan, thuc day
truc va » thuc vat, trung va
so sach » so sanh, bo sach, co sach
sach tu » sach thu, cach tu, sach ty
hieu ve » hieu va
dang xa » dang xay, lang xa, dang ha
tu dang » thu dang, tu dong, su dang
cua tre » cua te, cuu tre, cua triet

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach tu dang xa hoi. ((hieu ve) OR (hieu van)) nam ((truc va) or (thuc va)) thanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach tu dang xa hoi. ((hieu ve) OR (hieu van)) nam ((truc va) OR (thuc va)) thanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach tu dang xa hoi. ((hieu ve) OR (hieu van)) nam ((truc va) or (thuc va)) thanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach tu dang xa hoi. ((hieu ve) OR (hieu van)) nam ((truc va) or (thuc va)) thanh tai cua tre*.