Perhaps you should try some spelling variations:
thanh trung » thanh tung
chieu sach » chinh sach, chiet tach, chieu sang
hieu quang » thieu quang, hieu qua, diep quang
nhung cong » dung cong, thong cong, hang cong
hieu quan » hieu qua, lieu quan, thien quan
van thanh » ban thanh, van tuan
trung va » truong va, trang va, trung ha
cong van » cong vang, cong san, song van

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 ((chieu sach) OR (((hieu quang) OR (hieu quan)))) - thanh trung va nhung cong van thanh san~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((chieu sach) or (((hieu quang) OR (hieu quan)))) - thanh trung va nhung cong van thanh san~".
• Adding a wildcard symbol may retrieve word variants: ho ((chieu sach) or (((hieu quang) OR (hieu quan)))) - thanh trung va nhung cong van thanh san*.