Perhaps you should try some spelling variations:
"dung nhat toan snippets" » "dung nhan toan snippets", "dang nhat toan snippets", "dung nha toan snippets", "dung nhat tan snippets", "dung thuat toan snippets", "dung nhat trang 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.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("dung nhat toan 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 nhat toan snippets") OR ("dung java java snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( dung nhat toan snippets ) or ( dung java java snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("dung nhat toan snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))*.