Perhaps you should try some spelling variations:
thieu khang » chieu khong, thieu quang
thieu sang » chieu sang, thieu quang, hieu lang
hanh trinh » canh tranh, hanh chinh
nhung cong » dung cong, thong cong, hang cong
trinh va » trinh van, trinh vat, trinh ve
cong san » cong tac
than cao » toan cao, thai cao, than sao
than cap » khan cap, thanh lap, thanh cac

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