VI. kapitola. Problém čtyř barev
Rovinné grafy, GDML_Books, (1977), p. 79-91 / Harvested from
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@inbook{403910,
     title = {VI. kapitola. Probl\'em \v cty\v r barev},
     booktitle = {Rovinn\'e grafy},
     series = {GDML\_Books},
     publisher = {Mlad\'a fronta},
     address = {Praha},
     year = {1977},
     pages = {79-91},
     url = {http://dml.mathdoc.fr/item/403910}
}

 (éd.). VI. kapitola. Problém čtyř barev, dans Rovinné grafy, GDML_Books,  (1977), pp. 79-91. http://gdmltest.u-ga.fr/item/403910/