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:The same results were obtained by Winther and Nathalang [27] and by Knoll-K√∂hler [14], who did not determine any difference in the anaesthetic action profiles of a 2 and 4% solution of articaine or a 74-mM (=2.4% solution) and a 148-mM (=4
Category: