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:They include the ER, 595 with its rough and smooth domains (Sitia and Meldolesi, 1992), the neuronal 596 plasma membrane, with different compositions in the soma and dendrites 597 (Bradke and Dotti, 2000), and even the cytosol, where gradients of calcium 598 and other second messengers are…
Category: