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:This concurs with previous studies which have addressed this question (40, 53), the results of which have piqued the idea that estrogen receptor b, expressed in lung cancer cells, may be causal to this observation (54, 55), though various other hypotheses have also been suggested (56).
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