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2. N. Kh. Arutyunyan and A. V. Manzhirov, Contact Problems of Creep Theory (Inst. Mekh. NAN, Erevan, 1999).
3. N. Kh. Arutyunyan, A. V. Manzhirov, and V. E. Naumov, Contact Problems of Mechanics of Growing Bodies (Nauka, Moscow, 1991) [in Russian].
4. A. A. Kosmodem’yanskii, A Course of Theoretical Mechanics, Part II (Prosveshchenie, Moscow, 1966) [in Russian].
5. L. Collatz, Eigenvalue Problems with Technical Applications (Chelsea, New York, 1948; Nauka, Moscow, 1968).