@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/