Alkofer, R.Hecht, M. B.Roberts, C. D.Schmidt, S. M.Vinnik, D. V.2004-12-032004-12-0320012001http://hdl.handle.net/2003/152310.17877/DE290R-11286enThe American Physical SocietyPhysical Review Letters530Pair Creation and an X-Ray Free Electron Laser10.1103/PhysRevLett.87.193902article (journal)