@article{MAN_1952__125_160325,
     author = {S. Verblunsky},
     title = {On the curvature of level curves.},
     journal = {Mathematische Annalen},
     pages = {472--476},
     publisher = {mathdoc},
     volume = {125},
     year = {1952},
     zbl = {0051.06003},
     url = {http://geodesic.mathdoc.fr/item/MAN_1952__125_160325/}
}