Problém čtyř barev
Šišma, Pavel
Historie matematiky. II, GDML_Books, (1997), p. 169-180 / Harvested from
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@incollection{401043,
     title = {Probl\'em \v cty\v r barev},
     booktitle = {Historie matematiky. II},
     series = {GDML\_Books},
     publisher = {Prometheus},
     address = {Praha},
     year = {1997},
     pages = {169-180},
     url = {http://dml.mathdoc.fr/item/401043}
}

Šišma, Pavel. Problém čtyř barev, dans Historie matematiky. II, GDML_Books,  (1997), pp. 169-180. http://gdmltest.u-ga.fr/item/401043/