@misc{wikipedia2019,
    author = "{Wikipedia contributors}",
    title = "Free group --- {Wikipedia}{,} The Free Encyclopedia",
    year = "2019",
    howpublished = "\url{https://en.wikipedia.org/w/index.php?title=Free_group&oldid=882627634}",
    note = "[Online; accessed 21-February-2019]"
  }

@manual{sagemath2019,
  Key          = {SageMath},
  Author       = {{The \proglang{sage} Developers}},
  Title        = {\proglang{SageMath}, the \proglang{sage} mathematics software system (version 8.6)},
  url          = "https://www.sagemath.org",
  Year         = {2019}
}

@manual{GAP4,
    organization = "The \proglang{GAP}~Group",
        key          = "GAP",
    title        = "{\proglang{GAP} -- Groups, Algorithms, and Programming,
                    Version 4.10.0}",
    year         = 2018,
    url          = "https://www.gap-system.org"
    }
                  
@article{sympy2017,
 title = {\proglang{SymPy}: symbolic computing in \proglang{Python}},
 author = {Meurer, Aaron and others},
 year = 2017,
 month = jan,
 volume = 3,
 pages = {e103},
 journal = {PeerJ Computer Science},
 issn = {2376-5992},
 url = {https://doi.org/10.7717/peerj-cs.103},
 doi = {10.7717/peerj-cs.103}
}

@misc{hankin2022_freegroup,
  title = {The free group in \proglang{R}},
  doi = {10.48550/ARXIV.2212.05883},
  author = {Robin K. S. Hankin},
  publisher = {arXiv},
  year = {2022}
  }
                  
@Manual{rcore2022,
    title = {\proglang{R}: A Language and Environment for Statistical Computing},
    author = {{\proglang{R} Core Team}},
    organization = {\proglang{R} Foundation for Statistical Computing},
    address = {Vienna, Austria},
    year = {2022},
    url = {https://www.R-project.org/},
  }
