Perhaps you should try some spelling variations:
chieu hanh » chieu xanh, dieu hanh, chi hanh
thong cong » trong cong, tong cong, phong chong
hien hanh » dieu hanh
hanh tang » hanh trang, anh tang, hanh mang
tang cua » mang cua, hang cua, tang luan
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.

• Performing a fuzzy search may retrieve terms with similar spellings: theo ((chieu hanh) or (hien hanh)) - hanh tang cua ((thong cong) OR (thong thong)) bai toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: theo ((chieu hanh) OR (hien hanh)) - hanh tang cua ((thong cong) OR (thong thong)) bai toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo ((chieu hanh) or (hien hanh)) - hanh tang cua ((thong cong) OR (thong thong)) bai toan cau".
• Adding a wildcard symbol may retrieve word variants: theo ((chieu hanh) or (hien hanh)) - hanh tang cua ((thong cong) OR (thong thong)) bai toan cau*.