Perhaps you should try some spelling variations:
hieu tinh » chieu tinh, lieu tinh, kieu tinh
dung cong » dung trong
bang cong » dang cong, bang song, hang cong
doc hieu » toc thieu, hoc thieu, hoc hien
tranh va » tranh van, trang va, trinh va
toan cao » toan tap
toan ban » van ban

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 tinh - canh tranh va ((dung cong) or (bang cong)) dan ((toan cao) or (toan ban))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu tinh - canh tranh va ((dung cong) OR (bang cong)) dan ((toan cao) OR (toan ban)).
• Adding a wildcard symbol may retrieve word variants: doc hieu tinh - canh tranh va ((dung cong) or (bang cong)) dan ((toan cao) or (toan ban))*.