Perhaps you should try some spelling variations:
chiet tach » chieu sach
thanh tung » thanh cong
hoan thanh » hoang thanh, van thanh, quan thanh
hieu lang » chieu sang, hieu quang, nhieu tang
ban thanh » ban hanh, ban hang
tung cua » trung cua, tuong cua, dung cua
cua dung » cua dang, cua dong, qua dung

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 ((hieu lang) OR (chiet tach)) - thanh tung cua dung trong ((hoan thanh) OR (ban thanh)) lap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) or (chiet tach)) - thanh tung cua dung trong ((hoan thanh) OR (ban thanh)) lap~".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) or (chiet tach)) - thanh tung cua dung trong ((hoan thanh) OR (ban thanh)) lap*.