Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
thuc day » thuc dan, thuc vat
hai cua » thai cua, dai cua, hoi cua
thuc va » thuc vat, thuc dan
te sach » toc sach
tu nano » truc nano
tu nang » tru nang, tu nong, tu lang
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: te sach ((tu nang) OR (tu nano)) xa hoi. hieu van dao ((thuc va) or (thuc day)) hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((tu nang) OR (tu nano)) xa hoi. hieu van dao ((thuc va) OR (thuc day)) hanh hai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ((tu nang) OR (tu nano)) xa hoi. hieu van dao ((thuc va) or (thuc day)) hanh hai cua tre*".