@article{JRAM_1973__0262_0263_151373,
     author = {Heiko Harborth},
     title = {Ein {Extremalproblem} f\"ur {Gitterpunkte.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {356--360},
     publisher = {mathdoc},
     volume = {0262_0263},
     year = {1973},
     zbl = {0268.05008},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1973__0262_0263_151373/}
}