Perhaps you should try some spelling variations:
"trinh toan lua snippets" » "tinh toan lua snippets", "thanh toan lua snippets", "trinh han lua snippets", "trinh toan luan snippets", "trinh toan luat snippets", "trinh toan cua snippets"
"dung cong co snippets" » "dung trong co snippets", "dung dong co snippets", "dung cong cu snippets", "dung cong so 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: (((("trinh toan lua snippets") or ("dung cong co snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("trinh toan lua snippets") OR ("dung cong co snippets"))) OR ("locating bug code snippets")).
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• Adding a wildcard symbol may retrieve word variants: (((("trinh toan lua snippets") or ("dung cong co snippets"))) or ("locating bug code snippets"))*.