* Hainan Island incident 2001 EP-3E force down and seizure incident* [http://www.nsa.gov/about/_files/cryptologic_heritage/publications/coldwar/dangerous_business.pdf] U.S. Navy and National Reconnaissance During the Cold War* [http://www.nsa.gov/about/_files/cryptologic_heritage/publications/coldwar/dangerous_business.pdf] 1969 EC-121 shootdown incident and communication failures add immediate urgency to NSA establishment of new National SIGINT Operations Center
* [http://www.nsa.gov/about/_files/cryptologic_heritage/publications/coldwar/dangerous_business.pdf] U.S. Navy and National Reconnaissance During the Cold War* [http://www.nsa.gov/about/_files/cryptologic_heritage/publications/coldwar/dangerous_business.pdf] 1969 EC-121 shootdown incident and communication failures add immediate urgency to NSA establishment of new National SIGINT Operations Center