Perhaps you should try some spelling variations:
nhung cong » thong cong, hang cong, nhung don
hieu lang » chieu sang, hieu quang, nhieu tang
doanh cua » doanh luan
trung cua » truong cua, trung tuan, trung cap
dung cong » dung trong
doi hieu » doi chieu, doc hieu, doi hien
dan phan » doan phan, dan chan, van phan
phan dau » phan tu, hang dau

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doi hieu lang - hanh ((doanh cua) OR (trung cua)) ((nhung cong) OR (dung cong)) dan phan dau~.
• Adding a wildcard symbol may retrieve word variants: doi hieu lang - hanh ((doanh cua) or (trung cua)) ((nhung cong) or (dung cong)) dan phan dau*.