Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV–visible spectrometers during CINDI-2 - Kreher, K.; Van Roozendael, M.; Hendrick, F.; Apituley, A.; Dimitropoulou, E.; Frieß, U.; Richter, A.; Wagner, T.; Lampel, J.; Abuhassan, N.; Ang, L.; Anguas, M.; et al. (Atmos. Meas. Tech., 2020)