| September 11 Terrorist Attacks (American history, 2001) (preferred,English-P,D,P) |
| 9/11 Terrorist Attacks (American history, 2001) (English,U,P) |
| 911 Terrorist Attacks (American history, 2001) (English,U,P) |
| September 11 Attacks (American history, 2001) (English,U,P) |
| 9/11 Attacks (American history, 2001) (English,U,P) |
| Nine-Eleven Terrorist Attacks (American history, 2001) (English,U,P) |
| Sept. 11 Terrorist Attacks (American history, 2001) (English,U,P) |
| September 11 Terror Attacks (American history, 2001) (English,U,P) |
| September 11 Terrorism (American history, 2001) (English,U,P) |
| Terrorist Attacks, September 11, 2001 (American history, 2001) (English,U,P) |
| September 11 Terrorist Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) sh2001000147; accessed 19 May 2016 |
| 9/11 Terrorist Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| 911 Terrorist Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| September 11 Attacks (American history, 2001) |
| ................Encyclopedia Britannica Online (2002-) 19 December 2016 |
| 9/11 Attacks (American history, 2001) |
| ................Encyclopedia Britannica Online (2002-) |
| Nine-Eleven Terrorist Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| Sept. 11 Terrorist Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| September 11 Terror Attacks (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| September 11 Terrorism (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |
| Terrorist Attacks, September 11, 2001 (American history, 2001) |
| ................Library of Congress Authorities online (2002-) accessed 19 May 2016 |