Perhaps you should try some spelling variations:
thanh trung » thanh tung
thieu xanh » hieu manh, thien anh, thien danh
chieu xanh » chieu sach, chieu sang, chieu tinh
nhung cong » dung cong, thong cong, hang cong
trung cua » truong cua, trung tuan, trung cap
cua nhung » va nhung
tap toan » tap doan, tap quan
bai toan » bai tap

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

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