In low-pressure capacitive discharges the concept of Nonlinear Electron Resonance Heating (NERH) becomes important to enhance Ohmic dissipation. Particularly in geometrically asymmetric capacitive discharges (generation of a DC self-bias), the nonlinearities of the boundary plasma sheaths lead to a strongly non-sinusoidal radio frequency current. The Fourier spectra of such a current can indicate harmonics which are in resonance with the Plasma Series Resonance (PSR). The scenario of PSR was investigated by different models (e.g. zero-dimensional, spatially resolved), which assume that the bulk current is carried by the electron current and the sheath current by the displacement current. Although these models are able to resolve the nonlinear behavior between bulk and sheath a detailed kinetic picture is missing.