Perhaps you should try some spelling variations:
nhung phuong » dung phuong, nhu phuong, truong phuong
hieu quang » thieu quang, hieu quan, hieu qua
phuong dan » phuong danh, phuong doan, huong dan
doc hieu » toc thieu, hoc thieu, hoc hien
dan than » dan chan, ban than, van than
than cau » toan cau, phan cau, than cap

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 quang - manh ((trong van) OR (trong cac)) nhung phuong dan than cau~.
• Adding a wildcard symbol may retrieve word variants: doc hieu quang - manh ((trong van) or (trong cac)) nhung phuong dan than cau*.