Perhaps you should try some spelling variations:
"cong trinh co ban va cac tay co so viet nam" » "cong trinh do ban va cac tay co so viet nam", "cong trinh cong ban va cac tay co so viet nam", "cong trinh hoa ban va cac tay co so viet nam", "cong trinh co ban va cac cay co so viet nam", "cong trinh co ban va cac tac co so viet nam", "cong trinh co ban va cac tai co so viet nam", "cong trinh co ban va cac tay co hoc viet nam", "cong trinh co ban va cac ty co so viet nam", "cong trinh co ban va cac tay o so viet nam"
"cong trinh giao lan va cac cac co so viet nam" » "cong trinh gian lan va cac cac co so viet nam", "cong trinh giao dan va cac cac co so viet nam", "cong trinh giao la va cac cac co so viet nam", "cong trinh giao lan va cac cac co hoc viet nam", "cong trinh giao lan va cac cach co so viet nam", "cong trinh giao lan va ca cac co so viet nam", "cong trinh giao lan va cac bac co so viet nam", "cong trinh giao luan va cac cac co so viet nam", "cong trinh giao lanh va cac cac co so viet nam", "cong trinh giao lan van cac cac co so viet nam", "cong trinh giao lan va cac cac cong so viet nam"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("cong trinh co ban va cac tay co so viet nam") or ("cong trinh giao lan va cac cac co so viet nam"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("cong trinh co ban va cac tay co so viet nam") OR ("cong trinh giao lan va cac cac co so viet nam")).
• Removing quotes may allow a broader search: (( cong trinh co ban va cac tay co so viet nam ) or ( cong trinh giao lan va cac cac co so viet nam )).
• Adding a wildcard symbol may retrieve word variants: (("cong trinh co ban va cac tay co so viet nam") or ("cong trinh giao lan va cac cac co so viet nam"))*.