@article{HHA_2002_4_1_a2,
     author = {J. M. Casas and A. M. Vieites},
     title = {Some results on central extensions of crossed modules},
     journal = {Homology, homotopy, and applications},
     pages = {29--42},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {2002},
     doi = {10.4310/HHA.2002.v4.n1.a3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4310/HHA.2002.v4.n1.a3/}
}