Perhaps you should try some spelling variations:
"dung chung toan snippets" » "dung chung code snippets", "dung cong toan snippets", "dung trung toan snippets", "truong chung toan snippets", "dung chung ton snippets", "dung chung than snippets", "dung chung khoan snippets"
"locating bug core snippets" » "locating bug code snippets"
"dung java java snippets" » "dung va java snippets"

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("dung chung toan snippets") or ("dung java java snippets"))) or ("locating bug core snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("dung chung toan snippets") OR ("dung java java snippets"))) OR ("locating bug core snippets")).
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