Perhaps you should try some spelling variations:
"phong toan hoc snippets" » "phong thanh hoc snippets", "phong trao hoc snippets", "phong van hoc snippets", "phong toan khoa snippets", "phong hoa hoc 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 java java snippets") or ("phong toan hoc snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("dung java java snippets") OR ("phong toan hoc snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( dung java java snippets ) or ( phong toan hoc snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("dung java java snippets") or ("phong toan hoc snippets"))) or ("locating bug code snippets"))*.