Introducing a phase factor for the two-electron continuum representation Alexandr S. Zaytsev, Lorenzo Ugo Ancarani and Sergey A. Zaytsev Eur. Phys. J. D, 71 7 (2017) 177 Published online: 04 July 2017 DOI: 10.1140/epjd/e2017-70661-5