@article{DMGT_2000_20_2_a9,
     author = {Zelinka, Bohdan},
     title = {A note on periodicity of the 2-distance operator},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {267--269},
     publisher = {mathdoc},
     volume = {20},
     number = {2},
     year = {2000},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_2000_20_2_a9/}
}