Perhaps you should try some spelling variations:
trinh quan » tinh quang, trinh luat, trinh han
hieu lang » chieu sang, hieu quang, nhieu tang
trinh cua » tinh cua, trinh luat, trinh luan
dung cong » dung trong
hoi hieu » hoi phieu, hoi tieu, moi hieu
san toan » van toan, manh toan, xuan toan
dan toan » van toan, dan than, manh toan

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoi hieu lang - hanh ((trinh cua) or (trinh quan)) dung cong ((san toan) OR (dan toan)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoi hieu lang - hanh ((trinh cua) OR (trinh quan)) dung cong ((san toan) OR (dan toan)) cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoi hieu lang - hanh ((trinh cua) or (trinh quan)) dung cong ((san toan) OR (dan toan)) cau".
• Adding a wildcard symbol may retrieve word variants: hoi hieu lang - hanh ((trinh cua) or (trinh quan)) dung cong ((san toan) OR (dan toan)) cau*.