Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, nhung don
hieu lang » chieu sang, hieu quang, nhieu tang
hang cong » dang cong, hang nong, bang cong
doc hieu » toc thieu, hoc thieu, hoc hien
sinh cua » manh cua, sinh va
dinh cuu » dinh chi
van phan » van phong, van thanh, luan phan
phan cau » phan dau, phan cac, phan tu

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