@article{10_4064_cm_45_1_145_154,
     author = {Z. Majcher},
     title = {On k-closure operators in graphs. {II}},
     journal = {Colloquium Mathematicum},
     pages = {145--154},
     year = {1981},
     volume = {45},
     number = {1},
     doi = {10.4064/cm-45-1-145-154},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-45-1-145-154/}
}