Perhaps you should try some spelling variations:
hang doanh » hanh doanh, nhung doanh, van doanh
doanh luan » doanh nhan
thach thuc » thuc thuc, thanh thuy, cach thuc
hieu lang » chieu sang, hieu quang, nhieu tang
luan dang » luan nang, luan danh, luan dong
phong van » thong van, phong va, hong van
hoi hieu » hoi phieu, hoi tieu, moi hieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoi hieu lang - hang doanh luan dang ((phong van) or (phung van)) thach thuc~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoi hieu lang - hang doanh luan dang ((phong van) OR (phung van)) thach thuc.
• Adding a wildcard symbol may retrieve word variants: hoi hieu lang - hang doanh luan dang ((phong van) or (phung van)) thach thuc*.