Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
nhung cong » dung cong, thong cong, nhung don
hieu lang » chieu sang, nhieu tang, hieu van
hanh sinh » hanh tinh, hanh dinh, hinh sinh
hang cong » dang cong, hang nong, bang cong
van phan » van phong, van thanh, luan phan
phan cau » phan dau, phan cac, phan tu
sinh va » sinh vat, tinh va, dinh van

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: doc ((hieu lang) OR (hieu quang)) - hanh sinh va ((nhung cong) OR (hang cong)) van phan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu lang) OR (hieu quang)) - hanh sinh va ((nhung cong) or (hang cong)) van phan cau~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu lang) OR (hieu quang)) - hanh sinh va ((nhung cong) or (hang cong)) van phan cau*.