Perhaps you should try some spelling variations:
"september 14 attacks" » "september 1 attacks", "september 1.4 attacks", "september 11 attacks", "september 4 attacks"
"september 18 attacks" » "september 1 attacks", "september 11 attacks", "september 10 attacks", "september 11.8 attacks"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"september 14 attacks\") OR (\"september 18 attacks\"))".
• Removing quotes may allow a broader search: (( september 14 attacks ) OR ( september 18 attacks )).
• Adding a wildcard symbol may retrieve word variants: (("september 14 attacks") OR ("september 18 attacks"))*.