@book{PoTB,
  author    = {Martin Aigner and Gunter M. Ziegler},
  title     = {Proofs from THE BOOK},
  publisher = {Springer},
  year      = {1998}
}

@article{Sylvester,
    AUTHOR = {Chepuri, Sunita and Dowd, CJ and Hardt, Andrew and Michel,
              Gregory and Zhang, Sylvester W. and Zhang, Valerie},
     TITLE = {Arborescences of covering graphs},
   JOURNAL = {Algebr. Comb.},
  FJOURNAL = {Algebraic Combinatorics},
    VOLUME = {5},
      YEAR = {2022},
    NUMBER = {2},
     PAGES = {319--346}, 
       DOI = {10.5802/alco.212},
       URL = {https://doi.org/10.5802/alco.212},
}

@book{Fomin,
    AUTHOR = {Stanley, Richard P.},
     TITLE = {Enumerative combinatorics. {V}ol. 2},
    SERIES = {Cambridge Studies in Advanced Mathematics},
    VOLUME = {62},
      NOTE = {With a foreword by Gian-Carlo Rota and appendix 1 by Sergey
              Fomin},
 PUBLISHER = {Cambridge University Press, Cambridge},
      YEAR = {1999},
     PAGES = {xii+581 pp.},
       DOI = {10.1017/CBO9780511609589},
       URL = {https://doi.org/10.1017/CBO9780511609589},
}

@article{Galashin,
    AUTHOR = {Galashin, Pavel and Pylyavskyy, Pavlo},
     TITLE = {{$R$}-systems},
   JOURNAL = {Selecta Math. (N.S.)},
  FJOURNAL = {Selecta Mathematica. New Series},
    VOLUME = {25},
      YEAR = {2019},
    NUMBER = {2},
     PAGES = {Paper No. 22, 63 pp.},
       DOI = {10.1007/s00029-019-0470-2},
       URL = {https://doi.org/10.1007/s00029-019-0470-2},
}
}

@article{Tucker,
    AUTHOR = {Gross, Jonathan L. and Tucker, Thomas W.},
     TITLE = {Generating all graph coverings by permutation voltage
              assignments},
   JOURNAL = {Discrete Math.},
  FJOURNAL = {Discrete Mathematics},
    VOLUME = {18},
      YEAR = {1977},
    NUMBER = {3},
     PAGES = {273--283}, 
       DOI = {10.1016/0012-365X(77)90131-5},
       URL = {https://doi.org/10.1016/0012-365X(77)90131-5},
}