@article{DCG_1990__5_2_131102,
     author = {N.J.A. Sloane and R.L. Graham},
     title = {Penny-Packing and {Two-Dimensional} {Codes.}},
     journal = {Discrete & computational geometry},
     pages = {1--12},
     publisher = {mathdoc},
     volume = {5},
     number = {2},
     year = {1990},
     zbl = {0686.52010},
     url = {http://geodesic.mathdoc.fr/item/DCG_1990__5_2_131102/}
}