Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc dat » thuc vat, thuc dan, thuc day
dat hang » dat khanh, dat quang, tat thang
hang dai » hoang dai, hang tai, hang dau
su sach » so sach
vu sach » vu bach, vu khach
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (vu sach)) y nang ((x ho) or (o hoi)). hieu van nam thuc dat hang dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) y nang ((x ho) OR (o hoi)). hieu van nam thuc dat hang dai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) y nang ((x ho) or (o hoi)). hieu van nam thuc dat hang dai cua tre*.