About: http://webisa.webdatacommons.org/226822185

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Given a presentation of your group, with generators $x_i$ and relators $r_j$, there is a presentation of the crossed homomorphisms, as those crossed homomorphisms on the free group generated by the $x_i$ that annihilate the relators.
http://www.w3.org/ns/prov#wasQuotedFrom	mathoverflow.net