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3. S. M. Bak, “Existence of subsonic periodic traveling waves in a system of nonlinearly coupled nonlinear oscillators on the 2D lattice,” Mat. Komp’yut. Model., Ser. Fiz.-Mat. Nauk., Issue 10, 17–23 (2014).
4. S. M. Bak, “Existence of supersonic periodic traveling waves in a system of nonlinearly coupled nonlinear oscillators on the 2D lattice,” Mat. Komp’yut. Model., Ser. Fiz.-Mat. Nauk., Issue 12, 5–12 (2015).
5. S. M. Bak, “Existence of periodic traveling waves in a system of oscillators on the 2D lattice,” Mat. Stud., 35, No. 1, 60–65 (2011).