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:Release of a vesicle present in this domain cannot be impaired by a slow calcium buffer such as EGTA, not even in high millimolar concentrations (Adler et al., 1991; Nowycky and Pinter, 1993; Roberts, 1994; von Gersdorff and Matthews, 1994; Mennerick and
Matthews, 1996).
Category: