Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu xanh » chieu xanh, hieu manh, hieu nganh
doc hieu » toc thieu, hoc thieu, hoc hien
tranh va » tranh van, trang va, trinh va
tran van » luan van
tan toan » tan tran, van toan, dan toan
tap toan » tap doan, tap quan, bai toan

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 xanh - canh ((tranh va) or (tran van)) nhung cong ((tan toan) or (tap toan)) cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - canh ((tranh va) OR (tran van)) nhung cong ((tan toan) OR (tap toan)) cao.
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - canh ((tranh va) or (tran van)) nhung cong ((tan toan) or (tap toan)) cao*.