@article{IM_1988__93_2_143607,
     author = {William J. Floyd and Steven P. Plotnick},
     title = {Symmetries of planar growth functions.},
     journal = {Inventiones mathematicae},
     pages = {501--544},
     publisher = {mathdoc},
     volume = {93},
     number = {2},
     year = {1988},
     zbl = {0652.20052},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__93_2_143607/}
}