@article{JGAA_2018_22_3_a4,
     author = {David Eppstein},
     title = {Edge {Bounds} and {Degeneracy} of {Triangle-Free} {Penny} {Graphs} and {Squaregraphs}},
     journal = {Journal of Graph Algorithms and Applications},
     pages = {483--499},
     publisher = {mathdoc},
     volume = {22},
     number = {3},
     year = {2018},
     doi = {10.7155/jgaa.00463},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.7155/jgaa.00463/}
}