Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
chieu sang » chieu sach, chieu xanh, hieu lang
trung qua » trung quan, trong qua, truong quan
trung cua » truong cua, trung tuan, trung cap
dung cong » dung trong
cong dang » cong dong, cong dan, cong dung
dang hanh » dang thanh, ban hanh, dang van
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 qua) OR (trung cua)) 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 qua) OR (trung cua)) 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 qua) OR (trung cua)) dung cong dang hanh ban".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (chieu sang)) - hanh ((trung qua) OR (trung cua)) dung cong dang hanh ban*.