Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu tinh » chieu tinh, lieu tinh, kieu tinh
cua nhung » va nhung
doc hieu » toc thieu, hoc thieu, hoc hien
cong san » cong tac
phan dau » phan tu, hang dau
cac ban » cac dan, cac van, can ban
ban cua » ban quan

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 - cac ban cua nhung cong san ((phan lap) or (phan dau))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu tinh - cac ban cua nhung cong san ((phan lap) OR (phan dau)).
• Adding a wildcard symbol may retrieve word variants: doc hieu tinh - cac ban cua nhung cong san ((phan lap) or (phan dau))*.