1. A. G. Butkovskii, Control Methods for Systems with Distributed Parameters (Nauka, Moscow, 1975) [in Russian].
2. D. Matignon, Proc. Fractional Diff. Systems Models, Methods Appl. 5, 145–158 (1998).
3. A. N. Agadzhanov, Dokl. Math. 77, 98–101 (2008) [Dokl. Akad. Nauk 418, 583–586 (2008)].
4. A. N. Agadzhanov and A. G. Butkovskii, Dokl. Math. 77, 469–471 (2008) [Dokl. Akad. Nauk 420, 604–606 (2008)].
5. A. N. Agadzhanov and A. G. Butkovskii, in Problems of Analytic Mechanics and Stability Theory (Fizmatlit, Moscow, 2009), pp. 208–217 [in Russian].