FILOMAT, cilt.34, sa.6, ss.1755-1769, 2020 (SCI-Expanded)
The purpose of this paper is to obtain the notion of crossed modules over group-groupoids considering split extensions and prove a categorical equivalence between these types of crossed modules and
double group-groupoids. This equivalence enables us to produce various examples of double groupoids.
We also prove that crossed modules over group-groupoids are equivalent to crossed squares.