Alexander B. Bichkov and  Valery V. Smirnov,  Evaluation of Total Cross Section of Photo-Ionization of Helium in Weak Field on Base of Trajectory Method.   journal   = {International Journal of Physical and Mathematical Sciences}, [online]. World Academy of Science, Engineering and Technology.
    October 2013, vol. 83(11). 1556 - 1558
    [viewed 04 May 2024]. Available from: https://publications.waset.org/pdf/17248.