@article{VM_2001_3_1_a3,
     author = {Bruce D. Martin and Reza Sarhangi},
     title = {Symmetry, {Chemistry,} and {Escher's} {Tiles}},
     journal = {Visual Mathematics},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {2001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/VM_2001_3_1_a3/}
}