Double ionization of helium by fast electron impact A. Dorn, R. Moshammer, C.D. Schröter, T.J.M. Zouros, W. Schmitt, H. Kollmus, R. Mann and J. Ullrich J. Phys. IV France, 09 PR6 (1999) Pr6-89-Pr6-92 DOI: 10.1051/jp4:1999620
