  The far-infrared absorption in two-dimensional electron layers subject to
magnetic field of general orientation was studied theoretically. The Kubo
formula was employed to derive diagonal components of the magneto-conductivity
tensor of two-dimensional electron single-layers and double-layers. A parabolic
quantum well was used to model single-layer systems. Bilayer systems were
represented by a pair of tunnel-coupled, strictly two-dimensional quantum
wells. Obtained results were compared to experimental data.
