@article{DMGT_1996_16_1_a1,
     author = {Knor, Martin and Niepel, L'udov{\'\i}t},
     title = {Radii and centers in iterated line digraphs},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {17--26},
     publisher = {mathdoc},
     volume = {16},
     number = {1},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_1996_16_1_a1/}
}