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:Signalmediated MPO trafficking appears to be a likely mechanism of phase-matched electric field effects on neutrophils that accounts for changes in metabolism, oxidant production and DNA damage in response to weak electric fields (Kindzelskii and Petty 2000).
Category: