@article{JAC_2013__38_4_a5,
     author = {De Beule, Jan and Sziklai, P\'eter and Tak\'ats, Marcella},
     title = {On the structure of the directions not determined by a large affine point set},
     journal = {Journal of Algebraic Combinatorics},
     pages = {889--899},
     publisher = {mathdoc},
     volume = {38},
     number = {4},
     year = {2013},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JAC_2013__38_4_a5/}
}