Perhaps you should try some spelling variations:
trinh luan » trinh luat, trinh han, trinh toan
trinh quan » tinh quang, trinh luat, trinh han
hieu lang » chieu sang, hieu quang, nhieu tang
dung cong » dung trong
manh toan » thanh toan, anh tuan, tinh toan
hoi hieu » hoi phieu, hoi tieu, moi hieu
dan toan » van toan, dan than, xuan 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 luan) or (trinh quan)) dung cong ((dan toan) OR (manh toan)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoi hieu lang - hanh ((trinh luan) OR (trinh quan)) dung cong ((dan toan) OR (manh toan)) cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoi hieu lang - hanh ((trinh luan) or (trinh quan)) dung cong ((dan toan) OR (manh toan)) cau".
• Adding a wildcard symbol may retrieve word variants: hoi hieu lang - hanh ((trinh luan) or (trinh quan)) dung cong ((dan toan) OR (manh toan)) cau*.