Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Recently, analyses of archived African desert dust samples collected between 1812 and 1838 by colleagues of Charles Darwin demonstrated concentrations of bacteria and fungi of 104e105 CFU g 1 (Gorbushina et al., 2007).
Category: