Perhaps you should try some spelling variations:
"first graph sparsification document" » "first graph classification document", "first graph specification document", "first graph clarification document", "first graphs specification document", "first graph identification document", "first grade sparsification document", "first grand sparsification document"
"first _ sparsification document" » "first _ classification document", "first _ specification document", "first _ clarification document"
"first graph modification document" » "first graph specification document", "first graph clarification document", "first graph justification document", "first graph classification document", "first grade modification document", "first grand modification document"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("first graph sparsification document") OR ("first _ sparsification document"))) OR ("first graph modification document")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"first graph sparsification document\") OR (\"first _ sparsification document\"))) or (\"first graph modification document\"))".
• Removing quotes may allow a broader search: (((( first graph sparsification document ) OR ( first _ sparsification document ))) or ( first graph modification document )).
• Adding a wildcard symbol may retrieve word variants: (((("first graph sparsification document") OR ("first _ sparsification document"))) or ("first graph modification document"))*.