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:The ability of estrogens to modulate the expression of neuroprotective agents, namely the potent dopaminergic survival factor, GDNF, has been proven in both midbrain and hypothalamic cultures [10, 26].
Category: