Perhaps you should try some spelling variations:
"cong trinh duoc slippers" » "cong trinh doc slippers", "cong trinh duc slippers", "cong trinh quoc slippers", "cong trinh duoc slippery", "cong trinh duoc grippers"
"dung java java snippets" » "dung va java snippets"
"locating bug code snippets" » "locating bung code snippets", "locating bugs code snippets", "locating bug core snippets"

Try widening your search to All Fields.

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 duoc slippers") or ("dung java java snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("cong trinh duoc slippers") OR ("dung java java snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( cong trinh duoc slippers ) or ( dung java java snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("cong trinh duoc slippers") or ("dung java java snippets"))) or ("locating bug code snippets"))*.