Perhaps you should try some spelling variations:
khong cong » thong cong, chong cong, khong con
khong cang » thong cong, hong bang, khong dung
hieu xanh » chieu xanh, hieu manh, hieu nganh
doc hieu » toc thieu, hoc thieu, hoc hien
nang doc » nang luc
van toan » van tuan, van tan, van thanh
toan ban » van ban

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - ganh ((nang suat) OR (nang doc)) ((khong cong) OR (khong cang)) van toan ban~.
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - ganh ((nang suat) or (nang doc)) ((khong cong) or (khong cang)) van toan ban*.