Perhaps you should try some spelling variations:
cong cong » cong dong, trong cong, dung cong
bai toan » bai tap
tap tran » tap tranh, tan tran, tap trac
tap toan » tap doan, tap quan
te cong » tai cong, thi cong, thu cong
ke mo » ke o, ke do
ke co » ke o, de co
tuyen » truyen, quyen

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

• Performing a fuzzy search may retrieve terms with similar spellings: tuyen ((tap tran) or (((tap toan) OR (bai toan)))) thuy đe co ban ((ke mo) or (ke co)) te cong cong~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tuyen ((tap tran) OR (((tap toan) OR (bai toan)))) thuy đe co ban ((ke mo) OR (ke co)) te cong cong.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tuyen ((tap tran) or (((tap toan) OR (bai toan)))) thuy đe co ban ((ke mo) or (ke co)) te cong cong".
• Adding a wildcard symbol may retrieve word variants: tuyen ((tap tran) or (((tap toan) OR (bai toan)))) thuy đe co ban ((ke mo) or (ke co)) te cong cong*.