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
manh toan » thanh toan, anh tuan, tinh toan
doc hieu » toc thieu, hoc thieu, hoc hien
dan than » dan chan, ban than, van than

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

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