Jane's intelligence digest: the global early-warning service, P1, Jane's Information Group, 2009 Freedman, Benjamin; Levitt, Matthew (December 8, 2009).
2016년 5월 28일에 확인함.  Jane's intelligence digest: the global early-warning service, P1, Jane's Information Group, 2009 Freedman, Benjamin; Levitt, Matthew (2009년 12월 8일).