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
dan toan » dan than, manh toan, xuan toan
van toan » van tuan, van tan, van thanh
ho hieu » ho chieu, hoi hieu, nho hieu

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: ho hieu lang - hanh ((trinh cua) OR (trinh quan)) dung cong ((dan toan) OR (van toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho hieu lang - hanh ((trinh cua) or (trinh quan)) dung cong ((dan toan) OR (van toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: ho hieu lang - hanh ((trinh cua) or (trinh quan)) dung cong ((dan toan) OR (van toan)) cau*.