Perhaps you should try some spelling variations:
nhung cong » thong cong, hang cong, nhung don
hieu sang » chieu sang, hieu quang, nhieu tang
hieu lang » chieu sang, hieu quang, nhieu tang
tinh bang » tinh sang, tinh lang, tinh quang
dung cong » dung trong
dan than » dan chan, ban than, van than
than cau » toan cau, phan cau, than cap
bang va » hang va, ban va, trang va

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu sang) or (hieu lang)) - tinh bang va ((nhung cong) or (dung cong)) dan than cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu lang)) - tinh bang va ((nhung cong) OR (dung cong)) dan than cau.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu lang)) - tinh bang va ((nhung cong) or (dung cong)) dan than cau*.