"Overall concerns with the official version of 9/11 have been published and discussed by scholars and writers around the world including: Jim Mars, Nafeez Ahmed, Michael Ruppert, Cynthia McKinney, Barrie Zwicker, Webster Tarpley, Michel Chossudovsky and many others. The response to most has been to label these discussions as conspiracy theories unworthy of media coverage or further review. Pursuit of a critical analysis of these questions is undermined by the psychological barrier about 9/11 issues as threshold concepts - too awful to even consider."