Double ionization of helium with a convoluted quasi Sturmian approach Alexandr S. Zaytsev, Darya S. Zaytseva, Lorenzo Ugo Ancarani and Sergey A. Zaytsev Eur. Phys. J. D, 73 6 (2019) 111 Published online: 01 June 2019 DOI: 10.1140/epjd/e2019-90618-x