Perhaps you should try some spelling variations:
"dung luyen tre snippets" » "dung huyen tre snippets", "dung tuyen tre snippets", "dung nguyen tre snippets", "dung luyen tri snippets", "dung huyen tren snippets", "dung tuyen tren snippets"
"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: (((("dung luyen tre snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("dung luyen tre snippets") OR ("dung java java snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( dung luyen tre snippets ) or ( dung java java snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("dung luyen tre snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))*.