Harmonic morphisms of graphs and the Riemann-Hurwitz theorem

MEDNYKH, Alexander - NEDELA, Roman. Harmonic morphisms of graphs and the Riemann-Hurwitz theorem. In Doklady Mathematics. - Moscow : Pleiades Publishing, 2016. ISSN 1064-5624, 2016, vol. 93, no. 1, pp. 23-26. Dostupné na: https://doi.org/10.1134/S1064562416010105.