@article{BAG_1992__33_138504,
     author = {H.-D. Hecker and R. B\"ottcher},
     title = {Weitere {NP-schwere} {Probleme} f\"ur minimale {Polygon\"uberdeckungen}},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {71--76},
     publisher = {mathdoc},
     volume = {33},
     year = {1992},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/BAG_1992__33_138504/}
}