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 conclusion is consistent with previous results (7, 21, 22) that suggest that the increase in ALC produced by the b-adrenergic agonists isoproterenol and terbutaline is characterized by an increase in the proportion of the total sodium transport that is amiloride-sensitive.
Category: