Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu qua, diep quang
trinh chat » tinh chat, trinh luat
trinh phan » trinh quan, thanh phan, trinh toan
thong cong » trong cong, tong cong, thong thong
hieu quan » hieu qua, lieu quan, thien quan
trinh han » trinh quan
han dau » hang dau, phan dau, van dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: ho ((hieu quang) OR (hieu quan)) - hanh ((trinh chat) or (trinh phan)) thong cong trinh han dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((hieu quang) OR (hieu quan)) - hanh ((trinh chat) OR (trinh phan)) thong cong trinh han dau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu quang) OR (hieu quan)) - hanh ((trinh chat) or (trinh phan)) thong cong trinh han dau".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu quang) OR (hieu quan)) - hanh ((trinh chat) or (trinh phan)) thong cong trinh han dau*.