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:Therefore, the equilibrium and stability analysis of neural networks with time delays has been received much interest in recent years [2, 3, 4, 5, 6, 7, 18, 19, 20, 25, 24, 30, 21, 22, 23, 33].
Category: