@article{DMGT_2018_38_3_a9,
     author = {G\'orska, Joanna and Skupie\'n, Zdzis{\l}aw and Dziechci\'nska-Halamoda, Zyta and Majcher, Zofia and Michael, Jerzy},
     title = {Extremal {Irregular} {Digraphs}},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {791--800},
     publisher = {mathdoc},
     volume = {38},
     number = {3},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_2018_38_3_a9/}
}