During the first half of the 20th century, the factors that control learning and memory in animals were studied but the biological basis of the observations was poorly understood. (sciencemag.org)
The data basis of observations are total ozone columns measurements from three satellite borne instruments: the European satellite sensors GOME (ERS - 2), SCIAMACHY (ENVISAT), and GOME - 2 (METOP - A) are combined and added up to a continuous time series starting in June 1995. (esa-ozone-cci.org)