Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
chieu sang » chieu sach, chieu xanh, hieu lang
hanh trung » thanh trung, manh trung, danh trung
hanh trang » thanh trung, canh tranh, hanh trinh
dung cong » dung trong
cong dang » cong dong, cong dan, cong dung
dang hanh » dang thanh, ban hanh, dang van
qua dung » quang dung, su dung, qua song
hanh ban » thanh ban, hang ban, hanh san

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 sang)) - ((hanh trung) OR (hanh trang)) qua dung cong dang hanh ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (chieu sang)) - ((hanh trung) OR (hanh trang)) qua dung cong dang hanh ban.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu quang) or (chieu sang)) - ((hanh trung) OR (hanh trang)) qua dung cong dang hanh ban".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (chieu sang)) - ((hanh trung) OR (hanh trang)) qua dung cong dang hanh ban*.