Lobachevskii Journal of Mathematics
Lobachevskii Journal of Mathematics > 2018 > 39 > 4 > 524-532
Lobachevskii Journal of Mathematics > 2018 > 39 > 9 > 1188-1198
Lobachevskii Journal of Mathematics > 2018 > 39 > 4 > 524-532
Lobachevskii Journal of Mathematics > 2018 > 39 > 9 > 1188-1198