@article{MVK_2019_10_a3,
     author = {I. A. Kruglov and I. V. Cherednik},
     title = {On the existence of non-negative bases in subgroups of free groups of {Schreier} varieties},
     journal = {Matemati\v{c}eskie voprosy kriptografii},
     pages = {53--65},
     publisher = {mathdoc},
     volume = {10},
     year = {2019},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MVK_2019_10_a3/}
}