Perhaps you should try some spelling variations:
trinh quan » tinh quang, trinh luat, trinh han
nhung cong » dung cong, thong cong, hang cong
hieu lang » chieu sang, hieu quang, nhieu tang
trinh cua » tinh cua, trinh luat, trinh luan
doi hieu » doi chieu, doc hieu, doi hien
van toan » van tan, van thanh, manh toan
van tuan » van quan, van ban, anh tuan

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