Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
chieu sach » chinh sach, chiet tach, chieu sang
dung cong » dung trong
tung tam » trung tam, vung tam, tuong tac
dung tam » duong tam, dung tai, dung lam
cong tap » cuong tap, cong tac, cong tan
tap doan » tap quan
doan dau » doan dieu, phan dau, doan va

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 (chieu sach)) - manh ((tung tam) OR (dung tam)) dung cong tap doan dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (chieu sach)) - manh ((tung tam) OR (dung tam)) dung cong tap doan dau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu quang) or (chieu sach)) - manh ((tung tam) OR (dung tam)) dung cong tap doan dau".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (chieu sach)) - manh ((tung tam) OR (dung tam)) dung cong tap doan dau*.