Perhaps you should try some spelling variations:
"duong van hoe snippets" » "duong va hoe snippets", "luong va hoe snippets", "dang van hoe snippets", "duong van hoa snippets", "duong van hoc snippets", "duong van hieu 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.

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 hoe snippets") 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 hoe snippets") OR ("dung java java snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( duong van hoe snippets ) or ( dung java java snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("duong van hoe snippets") or ("dung java java snippets"))) or ("locating bug code snippets"))*.