Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, diep quang
trinh vat » trinh van, trinh luat, sinh vat
dung cong » dung trong
trinh va » trinh van, trinh ve, trinh vi
cong san » cong tac
san toan » van toan, dan toan, manh 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: hoc ((hieu quang) or (hieu qua)) - hanh ((trinh va) or (trinh vat)) dung cong san toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (hieu qua)) - hanh ((trinh va) OR (trinh vat)) dung cong san toan cau.
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (hieu qua)) - hanh ((trinh va) or (trinh vat)) dung cong san toan cau*.