Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
hieu sang » chieu sang, hieu lang, hieu quang
doc hieu » toc thieu, hoc thieu, hoc hien
vat tong » vat trong, va tong, vat dong
cong tac » cong ty
tac toan » tap toan, tam toan, hach toan
toan cau » toan cao, toan ban, toan tap

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 sang - hanh trinh ((vat tong) or (dot trong)) cong tac toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sang - hanh trinh ((vat tong) OR (dot trong)) cong tac toan cau*.