@article{PDMA_2013_6_a21,
     author = {N. V. Medvedeva and S. S. Titov},
     title = {On non-minimal perfect ciphers},
     journal = {Prikladnaya Diskretnaya Matematika. Supplement},
     pages = {42--44},
     publisher = {mathdoc},
     number = {6},
     year = {2013},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDMA_2013_6_a21/}
}