@article{AM2_1973__9_136329,
     author = {DAVID W. BOYD},
     title = {Improved {Bounds} for the {Disk-packing} {Constant}},
     journal = {Aequationes mathematicae},
     pages = {99--106},
     publisher = {mathdoc},
     volume = {9},
     year = {1973},
     zbl = {0255.52006},
     url = {http://geodesic.mathdoc.fr/item/AM2_1973__9_136329/}
}