@article{JGG_2010_14_1_JGG_2010_14_1_a5,
     author = {A. Dvoretsky },
     title = {Reflected {Surfaces} and {Their} {Directing} {Cones}},
     journal = {Journal for geometry and graphics},
     pages = {69--8},
     publisher = {mathdoc},
     volume = {14},
     number = {1},
     year = {2010},
     url = {http://geodesic.mathdoc.fr/item/JGG_2010_14_1_JGG_2010_14_1_a5/}
}