Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
trung quan » truong quan, trung tuan, truong quang
trong quan » thong quan, tong quan, thong quang
trong dung » thong dung, trung dung, trong rung
hieu lang » chieu sang, nhieu tang, hieu van
dung toan » dung doanh, dung thang, dung thanh
toan cao » toan ban, toan tap

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: theo ((hieu lang) OR (hieu quang)) - hanh ((trung quan) OR (trong quan)) dung trong dung toan cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo ((hieu lang) OR (hieu quang)) - hanh ((trung quan) or (trong quan)) dung trong dung toan cao~".
• Adding a wildcard symbol may retrieve word variants: theo ((hieu lang) OR (hieu quang)) - hanh ((trung quan) or (trong quan)) dung trong dung toan cao*.