Perhaps you should try some spelling variations:
thanh trung » thanh tung
nhieu tang » chieu sang, nhiet nang
dung cuong » dung cong, dung luong, dang cuong
hieu lang » chieu sang, hieu quang, hieu van
trung cua » truong cua, trung tuan, trung cap
cua dung » cua dang, cua dong, qua dung
tap toan » tap quan, bai toan
tap doan » tap quan

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: ho ((nhieu tang) OR (hieu lang)) - thanh trung cua dung cuong ((tap toan) OR (tap doan)) tap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((nhieu tang) or (hieu lang)) - thanh trung cua dung cuong ((tap toan) OR (tap doan)) tap~".
• Adding a wildcard symbol may retrieve word variants: ho ((nhieu tang) or (hieu lang)) - thanh trung cua dung cuong ((tap toan) OR (tap doan)) tap*.