Perhaps you should try some spelling variations:
thieu khang » chieu khong, thieu quang
thieu sang » chieu sang, thieu quang, hieu lang
nhung cong » dung cong, thong cong, hang cong
trang va » tran van
cong san » cong tac
san than » sang than, san thanh, ban than
than cao » toan cao, thai cao, than cap

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: hoc ((thieu sang) OR (thieu khang)) - hanh ((trang va) OR (hang va)) nhung cong san than cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thieu sang) or (thieu khang)) - hanh ((trang va) OR (hang va)) nhung cong san than cao~".
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu sang) or (thieu khang)) - hanh ((trang va) OR (hang va)) nhung cong san than cao*.