@article{01973835,
title = {The densest packing of 13 congruent circles in a circle.},
journal = {Beitr\"age zur Algebra und Geometrie},
volume = {44},
year = {2003},
pages = {431-440},
zbl = {1039.52015},
language = {en},
url = {http://dml.mathdoc.fr/item/01973835}
}
Fodor, Ferenc. The densest packing of 13 congruent circles in a circle.. Beiträge zur Algebra und Geometrie, Tome 44 (2003) pp. 431-440. http://gdmltest.u-ga.fr/item/01973835/