@article{10_4064_am_2_2_133_149,
     author = {J. Perkal},
     title = {Geometryczne wska\'zniki {\l}\k{a}k},
     journal = {Applicationes Mathematicae},
     pages = {133--149},
     publisher = {mathdoc},
     volume = {2},
     number = {2},
     year = {1954},
     doi = {10.4064/am-2-2-133-149},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/am-2-2-133-149/}
}