Perhaps you should try some spelling variations:
"truong toan hoc snippets" » "truong ton hoc snippets", "trong toan hoc snippets", "truong tan hoc snippets", "truong toan khoa snippets", "truong van hoc snippets", "truong 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.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("truong toan hoc snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("truong toan hoc snippets") OR ("dung java java snippets"))) OR ("locating bug code snippets")).
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• Adding a wildcard symbol may retrieve word variants: (((("truong toan hoc snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))*.