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, physiologically relevant 3D cell culture has been recognized as a potential bridge between traditional in vitro two-dimensional (2D) culture and in vivo animal studies.(7,8) It is thus critical to advance the development of scalable and affordable methods of producing 3D spheroids and/or organoids suitable for high-throughput cancer drug discovery.
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