In this chapter we derive the system characterizing the stationary oscillations of thin elastic plates with transverse shear deformation proposed in [56]. We assume that the body forces have a time-harmonic form, which we substitute into the full classical three-dimensional elasticity model to obtain a time-independent system. The so-called kinematic hypothesis is then applied and, by averaging over the thickness of the plate, we arrive at the desired system of equations. The boundary moment–stress operator is also defined.