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:Although phase 1 frequency decays rapidly and substantially, generating a wide range of instantaneous frequencies in a short period (Krans and Chapple 2005), the CoV was still less than those computed for phase 2 and 3 distributions.
Category: