@article{SLC_1986_15_a1,
     author = {Walter Kern and Alfred Wanka},
     title = {On a {Problem} about {Covering} {Lines} by {Squares}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {15},
     year = {1986},
     url = {http://geodesic.mathdoc.fr/item/SLC_1986_15_a1/}
}