Perhaps you should try some spelling variations:
chiet tach » chieu sach
thanh tung » thanh cong
nhung cong » dung cong, thong cong, nhung don
hieu lang » chieu sang, hieu quang, nhieu tang
hang cong » dang cong, hang nong, bang cong
san toan » van toan, dan toan, manh toan
toan cau » toan cao, toan ban, toan tap
tung va » trung va, tuong va, dung va

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

• Performing a fuzzy search may retrieve terms with similar spellings: doi ((chiet tach) or (hieu lang)) - thanh tung va ((nhung cong) OR (hang cong)) san toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doi ((chiet tach) OR (hieu lang)) - thanh tung va ((nhung cong) OR (hang cong)) san toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doi ((chiet tach) or (hieu lang)) - thanh tung va ((nhung cong) OR (hang cong)) san toan cau".
• Adding a wildcard symbol may retrieve word variants: doi ((chiet tach) or (hieu lang)) - thanh tung va ((nhung cong) OR (hang cong)) san toan cau*.