Hal Roberts; Ethan Zuckerman; John Palfrey. 2007 Circumvention Landscape Report. Berkman Center of Law and Society, Harvard University. 2009-03-05. (原始内容存档于2012-10-03).
Hal Roberts; Ethan Zuckerman; John Palfrey. 2007 Circumvention Landscape Report. Berkman Center of Law and Society, Harvard University. 2009-03-05. (原始内容存档于2012-10-03).