Perhaps you should try some spelling variations:
pdung cong » phung cong, dang cong, duong cong
hieu sang » chieu sang, hieu lang, hieu quang
hanh tran » hanh trang, thanh tran, hanh tram
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
tran van » luan van
dan than » dan chan, ban than, van than
than cap » khan cap, thanh lap, thanh cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc hieu sang - hanh tran van ((dung cong) or (pdung cong)) dan than cap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sang - hanh tran van ((dung cong) OR (pdung cong)) dan than cap.
• Adding a wildcard symbol may retrieve word variants: doc hieu sang - hanh tran van ((dung cong) or (pdung cong)) dan than cap*.