@article{CHEB_2011_12_2_a13,
     author = {S. V. Syrovatskaya},
     title = {On $P$-algebras based on 4-systems},
     journal = {\v{C}eby\v{s}evskij sbornik},
     pages = {110--117},
     year = {2011},
     volume = {12},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CHEB_2011_12_2_a13/}
}