N. Kuznetsov, M. Yu. Lobachev, M. V. Yuldashev, R. V. Yuldashev, S. I. Volskiy, D. A. Sorokin, “On the generalized Gardner problem for phase-locked loops in electrical grids”, Dokl. RAN. Math. Inf. Proc. Upr., 498 (2021), 71–75; Dokl. Math., 103:3 (2021), 157–161
