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:Apoptosis can be distinguished from necrosis by its involvement of endonuclease activation leading to internucleosomal doublestranded chromatin (DNA) breaks and by the absence of the early cell membrane damage characteristic of necrosis (47, 48).
Category: