@manual{ AutoDoc,
  author =           {Gutsche, S. and Horn, M.},
  title =            {{AutoDoc  \texttt{\symbol{45}}  Generate documentation
                      from GAP source code (Version 2017.09.15)}},
  year =             {2017},
  note =             {GAP                   package,                   \href
                      {https://github.com/gap-packages/AutoDoc}
                      {\texttt{https://github.com/}\discretionary
                      {}{}{}\texttt{gap\texttt{\symbol{45}}packages/}\discretionary
                      {}{}{}\texttt{AutoDoc}}},
  printedkey =       {GH17}
}
@manual{ GAPDoc,
  author =           {L{\"u}beck, F. and Neunh{\"o}ffer, M.},
  title =            {{GAPDoc (version 1.6)}},
  organization =     {RWTH Aachen},
  year =             {2017},
  note =             {GAP                   package,                   \href
                      {https://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc/index.html}
                      {\texttt{https://www.math.rwth\texttt{\symbol{45}}aachen.de/}\discretionary
                      {}{}{}\texttt{\texttt{\symbol{126}}Frank.Luebeck/}\discretionary
                      {}{}{}\texttt{GAPDoc/}\discretionary
                      {}{}{}\texttt{index.html}}},
  printedkey =       {LN17}
}
@manual{ GitHubPagesForGAP,
  author =           {Horn, M.},
  title =            {{GitHubPagesForGAP \texttt{\symbol{45}} a GitHub Pages
                      generator for GAP packages}},
  volume =           {0.2},
  year =             {2017},
  note =             {GAP                   package,                   \href
                      {https://gap-system.github.io/GitHubPagesForGAP/}
                      {\texttt{https://gap\texttt{\symbol{45}}system.github.io/}\discretionary
                      {}{}{}\texttt{GitHubPagesForGAP/}}},
  printedkey =       {Hor17}
}
@manual{ alp3,
  author =           {Alp, M. and Odabas, A. and Uslu, E. O. and Wensley, C.
                      D.},
  title =            {{XMod:           Crossed          Modules          and
                      Cat1\texttt{\symbol{45}}groups in GAP}},
  volume =           {2.63},
  year =             {2017},
  note =             {GAP                   package,                   \href
                      {https://gap-packages.github.io/xmod/}
                      {\texttt{https://gap\texttt{\symbol{45}}packages.github.io/}\discretionary
                      {}{}{}\texttt{xmod/}}},
  printedkey =       {AOUW17}
}
@article{ alp2,
  author =           {Alp, M. and Wensley, C. D.},
  title =            {Enumeration  of  cat1\texttt{\symbol{45}}groups of low
                      order},
  journal =          {Int. J. Algebra and Computation},
  volume =           {10},
  year =             {2000},
  pages =            {407\texttt{\symbol{45}}\texttt{\symbol{45}}424},
  printedkey =       {AW00}
}
@article{ arvasi2,
  author =           {Arvasi, Z. and Porter, T.},
  title =            {Simplicial  and  Crossed  Resolutions  of  Commutative
                      Algebras},
  journal =          {J. Algebra},
  volume =           {181},
  year =             {1996},
  pages =            {426\texttt{\symbol{45}}\texttt{\symbol{45}}448},
  printedkey =       {AP96}
}
@article{ arvasi3,
  author =           {Arvasi, Z. and Porter, T.},
  title =            {Freeness Conditions for $2$\texttt{\symbol{45}}Crossed
                      Modules of Commutative Algebras},
  journal =          {Applied Categorical Structures},
  volume =           {6},
  year =             {1998},
  pages =            {455\texttt{\symbol{45}}\texttt{\symbol{45}}471},
  printedkey =       {AP98}
}
@article{ arvasi4,
  author =           {Arvasi, Z. and Ege, U.},
  title =            {Annihilators, multipliers and crossed modules},
  journal =          {Applied Categorical Structures},
  volume =           {11},
  year =             {2003},
  pages =            {487\texttt{\symbol{45}}\texttt{\symbol{45}}506},
  printedkey =       {AE03}
}
@article{ arvasi_odabas,
  author =           {Arvasi, Z. and Odabas, A.},
  title =            {Computing  2\texttt{\symbol{45}}Dimensional  Algebras:
                      Crossed Modules and Cat1\texttt{\symbol{45}}algebras},
  journal =          {Journal of Algebra and Its Applications},
  volume =           {15},
  year =             {2016},
  pages =            {1650185 (12 pages)},
  printedkey =       {AO16}
}
@inproceedings{ brown1,
  author =           {Brown, R.},
  booktitle =        {Low Dimensional Topology},
  title =            {Higher Dimensional Group Theory},
  publisher =        {London Mathematical Society},
  series =           {London Math. Soc. Lecture Note Series},
  volume =           {48},
  year =             {1982},
  printedkey =       {Bro82}
}
@article{ brown2,
  author =           {Brown, R.},
  title =            {From groups to groupoids: a brief survey},
  journal =          {Bull. London Math. Soc.},
  volume =           {19},
  year =             {1987},
  pages =            {113\texttt{\symbol{45}}\texttt{\symbol{45}}134},
  printedkey =       {Bro87}
}
@article{ ellis1,
  author =           {Ellis, G. J.},
  title =            {Higher Dimensional Crossed Modules of Algebras},
  journal =          {J. Pure and Appl. Algebra},
  volume =           {52},
  year =             {1988},
  pages =            {277\texttt{\symbol{45}}\texttt{\symbol{45}}282},
  printedkey =       {Ell88}
}
@article{ loday,
  author =           {Loday, J.\texttt{\symbol{45}}L.},
  title =            {Spaces           with           finitely          many
                      non\texttt{\symbol{45}}trivial homotopy groups},
  journal =          {J. App. Algebra},
  volume =           {24},
  year =             {1982},
  pages =            {179\texttt{\symbol{45}}\texttt{\symbol{45}}202},
  printedkey =       {Lod82}
}
@phdthesis{ mosa,
  author =           {Mosa, G. H.},
  title =            {Higher dimensional algebroids and crossed complexes},
  school =           {University of Wales, Bangor (U.K.)},
  year =             {1986},
  printedkey =       {Mos86}
}
@phdthesis{ aodabas1,
  author =           {Odabas, A.},
  title =            {Crossed Modules of Algebras with GAP},
  school =           {Osmangazi University, Eskisehir},
  year =             {2009},
  printedkey =       {Oda09}
}
@phdthesis{ shammu1,
  author =           {Shammu, N. M.},
  title =            {Algebraic  and  categorical structure of categories of
                      crossed modules of algebras},
  school =           {University of Wales, Bangor (U.K.)},
  year =             {1992},
  printedkey =       {Sha92}
}
@article{ porter1,
  author =           {Porter, T.},
  title =            {Some  categorical  results  in  the  theory of crossed
                      modules in commutative algebras},
  journal =          {J. Algebra},
  volume =           {109},
  year =             {1987},
  pages =            {415\texttt{\symbol{45}}\texttt{\symbol{45}}429},
  printedkey =       {Por87}
}
@article{ whitehead,
  author =           {Whitehead, J. H. C.},
  title =            {Combinatorial homotopy {I}{I}},
  journal =          {Bull. Amer. Math. Soc.},
  volume =           {55},
  year =             {1949},
  pages =            {453\texttt{\symbol{45}}\texttt{\symbol{45}}496},
  printedkey =       {Whi49}
}