@article{PDMA_2014_7_a23,
     author = {S. M. Ratseev},
     title = {Conditions for the existence of perfect ciphers with a~fixed set of parameters},
     journal = {Prikladnaya Diskretnaya Matematika. Supplement},
     pages = {54--56},
     publisher = {mathdoc},
     number = {7},
     year = {2014},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDMA_2014_7_a23/}
}