Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu lang » chieu sang, hieu quang, nhieu tang
cua nhung » va nhung
doc hieu » toc thieu, hoc thieu, hoc hien
anh tang » anh bang, anh dang, anh nang
san van » tan van, tran van, dang van
luan » quan, lan

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 - ((anh tang) OR (nhanh quang)) cua nhung cong ((san van) OR (luan van)) ban~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu lang - ((anh tang) or (nhanh quang)) cua nhung cong ((san van) OR (luan van)) ban~".
• Adding a wildcard symbol may retrieve word variants: doc hieu lang - ((anh tang) or (nhanh quang)) cua nhung cong ((san van) OR (luan van)) ban*.