1. A. M. Blokhin, ?Estimation of the energy integral of a mixed problem for equations of Gas Dynamics with boundary conditions on the shock wave,? Sib. Mat. Zh.,22, No. 4, 23?51 (1981).
2. A. M. Blokhin, ?A mixed problem for a system of equations of Acoustics with boundary conditions on the shock wave,? Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Tekh. Nauk13, No. 3, 25?33 (1979).
3. A. M. Blokhin, On the Well-Posedness of a Mixed Problem for a System of Equations of Acoustics with Boundary Conditions on the Shock Wave [in Russian], Preprint of the Computer Center of the Siberian Branch of the Academy of Sciences of the USSR, 141, Novosibirsk (1979).
4. S. L. Sobolev, Certain Applications of Functional Analysis in Mathematical Physics [in Russian], Izd. Leningr. Gos. Univ., Leningrad (1950).