The strong-field approximation (SFA) is widely used to calculate photoelectron spectra (PES) in the field of strong laser-matter interaction. We investigate different extensions of that theory to analyze spectral features beyond the scope of the plain SFA. We consider different systems where additional forces influence the emitted electron. Appropriate methods are derived and used to calculate PES. The results are compared to numerical solutions of the time-dependent Schrödinger equation or results from the literature and analyzed in terms of quantum trajectories.<eng>
