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:Similar discrepancies between PCR and culturing methods have been found by other authors (4,8,11) and may result from a low estimate of DNA in the CFU method from unculturable or slow-growing bacteria, nonviable cells, or free DNA.
Category: