Perhaps you should try some spelling variations:
dong thuan » don thuan, dong chuan, dong thuong
hieu lang » chieu sang, hieu quang, nhieu tang
hanh dong » anh dong, ha dong
long cong » luong cong, tong cong, long tong
cong cong » cong dong, trong cong, dung cong
doc hieu » toc thieu, hoc thieu, hoc hien
tan toan » tan tran, tap toan, van toan
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 lang - hanh dong thuan ((long cong) or (cong cong)) tan toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu lang - hanh dong thuan ((long cong) OR (cong cong)) tan toan ban*.