Perhaps you should try some spelling variations:
"trinh cac viet slippers" » "trinh cau viet slippers", "trinh chat viet slippers", "trinh chao viet slippers", "trinh cach viet slippers", "trinh bac viet slippers", "trinh ca viet slippers", "trinh cac viet slippery", "trinh cac viet grippers"
"dung dung code snippets" » "duong dung code snippets", "ung dung code snippets", "dung ung code snippets", "dung dung cong snippets", "dung dung co snippets", "dung dung de snippets"
"locating bug code snippets" » "locating bung code snippets", "locating bugs code snippets"

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("trinh cac viet slippers") or ("dung dung code snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("trinh cac viet slippers") OR ("dung dung code snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( trinh cac viet slippers ) or ( dung dung code snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("trinh cac viet slippers") or ("dung dung code snippets"))) or ("locating bug code snippets"))*.