@article{PDM_2008_1_a9,
     author = {N. N. Tokareva},
     title = {Quadratic approximations of the special type for the 4-bit permutations in {S-boxes}},
     journal = {Prikladna\^a diskretna\^a matematika},
     pages = {50--54},
     publisher = {mathdoc},
     number = {1},
     year = {2008},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDM_2008_1_a9/}
}