The method of characteristics for hyperbolic boundary value problems on the plane. Vorob'eva, E.V.; Romanovskij, R.K. — 2000 Siberian Mathematical Journal
Exponential dichotomy of linear systems with almost periodic matrices. Romanovskij, R.K.; Bel'gart, L.V. — 2009 Sibirskij Matematicheskij Zhurnal
Stability of solutions to the Cauchy problem for a plane hyperbolic system with time-periodic coefficients. RomanovskiJ, R.K.; Mendziv, M.V. — 2007 Sibirskij Matematicheskij Zhurnal