Marshall Hall's theorem through finite cores

Source: url:https://github.com/arthur742ramos/marshallhalltheorem Authors: Arthur Freitas Ramos, David Barros Hulak, Ruy J. G. B. de Queiroz Status: verified Main declarations: MarshallHall.marshallHall, MarshallHall.rank_freeProduct_eq_add Tags: group-theory MSC: 20E07, 20F65, 05C25