Stojkovikj, Natasha, Kocaleva, Mirjana, Martinovska Bande, Cveta, Stojanova, Aleksandra, AND Zlatanovska, Biljana. " Application of the Four-Color Theorem for coloring a city map" Balkan Journal of Applied Mathematics and Informatics [Online], Volume 3 Number 1 (24 June 2020)