Perhaps you should try some spelling variations:
chieu sang » chieu xanh, hieu lang, nhieu tang
chieu sach » chinh sach, chiet tach, chieu xanh
hanh tranh » canh tranh, hanh trinh, hanh trang
tranh cua » doanh cua, manh cua
cua thong » cua thuong, cua khong, cua tong
tap toan » tap quan, bai toan
tap doan » tap quan

You may be able to get more results by adjusting your search query.

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