Conservation laws for electron vortices in strong-field ionisation Yuxin Kang, Emilio Pisanty, Marcelo Ciappina, Maciej Lewenstein, Carla Figueira de Morisson Faria and Andrew S. Maxwell Eur. Phys. J. D, 75 7 (2021) 199 Published online: 09 July 2021 DOI: 10.1140/epjd/s10053-021-00214-4