Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
cong thanh » dong thanh, cong trinh, cong tan
hieu lang » chieu sang, nhieu tang, hieu van
cong manh » cong danh, duong manh, hoang manh
tranh va » tranh van, trang va, trinh va
toan cao » toan ban, toan tap
va nang » van nang, da nang, cam nang

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 lang) OR (hieu quang)) - canh tranh va nang ((cong manh) or (cong thanh)) toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((hieu lang) OR (hieu quang)) - canh tranh va nang ((cong manh) OR (cong thanh)) toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) OR (hieu quang)) - canh tranh va nang ((cong manh) or (cong thanh)) toan cao".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) OR (hieu quang)) - canh tranh va nang ((cong manh) or (cong thanh)) toan cao*.