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:These data, in agreement with our earlier work (33), support the hypothesis that the antitumor activity is related specifically to a-CbT and not to some unknown substances present with the purified natural toxin, and reinforced our prior results showing that a-CbT did not cause any cell death among A549-si-mRNA (a7-nAChR) cells (33), sustaining the postulation that its antitumoral activity passes through a7-nAChR inhibition.
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