Perhaps you should try some spelling variations:
"dung sach toan snippets" » "dung sach code snippets", "duong sach toan snippets", "dung sai toan snippets", "dung cac toan snippets", "dung hach toan snippets", "dung sach tranh snippets", "dung hoach toan snippets"
"locating bug core snippets" » "locating bug code snippets"
"dung java java snippets" » "dung va java 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 java java snippets") or ("dung sach toan snippets"))) or ("locating bug core snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("dung java java snippets") OR ("dung sach toan snippets"))) OR ("locating bug core snippets")).
• Removing quotes may allow a broader search: (((( dung java java snippets ) or ( dung sach toan snippets ))) or ( locating bug core snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("dung java java snippets") or ("dung sach toan snippets"))) or ("locating bug core snippets"))*.