@article{CMJ_2006__56_1_a13,
     author = {Li, Jinjin and Lin, Shou},
     title = {$k$-systems, $k$-networks and $k$-covers},
     journal = {Czechoslovak Mathematical Journal},
     pages = {239--245},
     publisher = {mathdoc},
     volume = {56},
     number = {1},
     year = {2006},
     mrnumber = {2207015},
     zbl = {1164.54359},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/item/CMJ_2006__56_1_a13/}
}