Perhaps you should try some spelling variations:
thieu khang » chieu khong, thieu quang
chieu sang » chieu sach, chieu xanh, hieu lang
thanh tung » thanh cong
thong cong » trong cong, tong cong, phong chong
tung cua » trung cua, tuong cua, dung cua
dan toan » van toan, dan than, manh toan
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 khang) OR (chieu sang)) - thanh tung cua ((thong cong) OR (thong thong)) dan toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thieu khang) or (chieu sang)) - thanh tung cua ((thong cong) OR (thong thong)) dan toan cau~".
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu khang) or (chieu sang)) - thanh tung cua ((thong cong) OR (thong thong)) dan toan cau*.