Authors: S Neppl; R Ernstorfer; A L Cavalieri; C Lemell; G Wachter; E Magerl; E M Bothschafter; M Jobst; M Hofstetter; U Kleineberg; J V Barth; D Menzel; J Burgdörfer; P Feulner; F Krausz; R Kienberger Journal: Nature Date: 2015-01-15 Impact factor: 49.962