Until today dispersion analysis could not be successfully applied to evaluate oscillator parameters of modes that have their transition moments perpendicular to the surface of an anisotropic crystal or a layered medium. The main reason for this failure is that while such modes generate maxima in the external reflection spectra, which are obtained with polarized light parallel to the plane of incidence under nonzero angles of incidence, the positions of these maxima do not allow us to unambiguously trace back the oscillator positions. In contrast, total internal reflection of parallel polarized light generates minima at spectral positions close to the oscillator frequency. Starting from this observation, we found that a combined evaluation of external and total internal reflection spectra by dispersion analysis allows us to gain the oscillator parameters of perpendicular modes unambiguously.