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:Images were captured with the Attovision software using the epifluorescence microscope Pathway (Becton Dickinson) and measured the signals using ImageJ (open source from National Cancer Institute, NIH) with custom-made macros [48].
Category: