In most cases, the GW+BSE optical gaps are within 0.2 eV or less from experimental values. The GW+BSE absorption spectra are validated by comparison to thin film experimental data for representative materials. For an anisotropic crystal the absorbance depends on the polarization direction of the incident light. Most absorption experiments are performed on polycrystalline samples and even in experiments performed on single crystals the crystallographic orientation of the sample with respect to the polarization of the incident light is often unknown. This introduces some uncertainties in the comparison with experiments. We calculate the absorbance for light polarized along the a, b, and c lattice vectors and normalize the maximum of the total absorbance to one. The results are shown in Figure . For 1,2-benzanthracene (BEANTR), coronene (CORONE01), and hexabenzo(bc,ef,hi,kl,no,qr)coronene (HBZCOR) the agreement of the GW+BSE spectra with experiment is very good. For chrysene (CRYSEN01), p-terphenyl (TERPHE02), and triphenylene (TRIPHE12) the agreement is more qualitative.