@article{10_4153_CMB_1968_080_1,
     author = {Oler, N.},
     title = {Elements of {Packing} and {Covering}},
     journal = {Canadian mathematical bulletin},
     pages = {671--677},
     year = {1968},
     volume = {11},
     number = {5},
     doi = {10.4153/CMB-1968-080-1},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1968-080-1/}
}