Perhaps you should try some spelling variations:
"duong van trac slippers" » "duong va trac slippers", "luong va trac slippers", "dang van trac slippers", "duong van thac slippers", "duong van tra slippers", "duong van trac slippery", "duong van trac grippers"
"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.

You may be able to get more results by adjusting your search query.

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