Perhaps you should try some spelling variations:
phuong thong » phuong trong, thong thong, phuong dong
thanh dung » thanh duong, thanh tung, thanh hung
hieu sang » chieu sang, hieu lang, hieu quang
doc hieu » toc thieu, hoc thieu, hoc hien
dung cua » dung luan, dung cho
dan than » dan chan, van than, dan toan
ban than » ban thanh, van thanh, ban hang

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 sang - thanh dung cua ((phuong thong) OR (phuong hoang)) ((dan than) OR (ban than)) cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu sang - thanh dung cua ((phuong thong) or (phuong hoang)) ((dan than) OR (ban than)) cao~".
• Adding a wildcard symbol may retrieve word variants: doc hieu sang - thanh dung cua ((phuong thong) or (phuong hoang)) ((dan than) OR (ban than)) cao*.