Perhaps you should try some spelling variations:
dung phuong » dung thuong, bang phuong, dung chung
hieu quang » thieu quang, hieu quan, hieu qua
phuong dan » phuong danh, phuong doan, huong dan
hieu sang » chieu sang, hieu lang, nhieu tang
trang va » tran van
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap

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) or (hieu quang)) - hanh ((trang va) or (hang va)) dung phuong dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu quang)) - hanh ((trang va) OR (hang va)) dung phuong dan toan cau.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu quang)) - hanh ((trang va) or (hang va)) dung phuong dan toan cau*.