Opo lidar sounding of trace atmospheric gases in the 3 – 4 μm spectral rangeOleg A. Romanovskii, Sergey A. Sadovnikov, Olga V. Kharchenko and Semen V. YakovlevEPJ Web Conf., 176 (2018) 05016DOI: https://doi.org/10.1051/epjconf/201817605016