Perhaps you should try some spelling variations:
thieu khang » chieu khong, thieu quang
thieu sang » chieu sang, thieu quang, hieu lang
dang cuong » dang cong, quang cuong, dang thuong
tang cuong » nang luong
tranh cua » doanh cua, manh cua
bai toan » bai tap
toan cau » toan cao, toan ban, toan tap

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)) - canh tranh cua ((dang cuong) OR (tang cuong)) bai toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thieu sang) OR (thieu khang)) - canh tranh cua ((dang cuong) or (tang cuong)) bai toan cau~".
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu sang) OR (thieu khang)) - canh tranh cua ((dang cuong) or (tang cuong)) bai toan cau*.