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:Of note, there are other studies showing that the mRNA level of BNP was not elevated at a compensatory hypertrophic stage, but only at a decompensated stage in Dahl salt-sensitive rats (46, 56).
Category: