Perhaps you should try some spelling variations:
dang khanh » dang hanh, dang thanh, dan khanh
hieu tinh » chieu tinh, lieu tinh, kieu tinh
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
trang va » hang va
tran van » luan van
dan khan » dan khanh, dan chan, dan than

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 tinh - thanh ((trang va) OR (tran van)) dung cong ((dan khan) OR (dang khanh)) cap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu tinh - thanh ((trang va) OR (tran van)) dung cong ((dan khan) or (dang khanh)) cap~".
• Adding a wildcard symbol may retrieve word variants: doc hieu tinh - thanh ((trang va) OR (tran van)) dung cong ((dan khan) or (dang khanh)) cap*.