Rayleigh lidar observation of a warm stratopause over a tropical site, Gadanki (13.5° N; 79.2° E) - Sivakumar, V.; Morel, B.; Bencherif, H.; Baray, J. L.; Baldy, S.; Hauchecorne, A.; Rao, P. B. (Atmos. Chem. Phys., 2004)