1. Bishop, R.E.D. “Longitudinal Waves in Beams”, Aeronaut. Q. 3 (2), 280–293 (1952).
2. Ptashnik, B.I. Ill-posed Problems for Partial Differential Equations (Naukova Dumka, Kiev, 1984) [in Russian].
3. Nakhushev, A.M. Equations of Mathematical Biology (Vysshaya Shkola, Moscow, 1995) [in Russian].
4. Demidenko, G.V., Uspenskii, S.V. Partial Differential Equations and Systems not Solvable with Respect to the Highest-Order Derivative, Pure and Appl. Math. 256 (Marcel Dekker, New York, 1998).
5. Algazin, S.D., Kiiko, I.A. Flutter of Plates and Shells (Nauka, Moscow, 2006) [in Russian].