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:DSF are characterized by smaller chromatic dispersion and higher Raman scattering coefficient than standard SMF (showing similar loss coefficients), and hence they have been found more suitable for long-range Raman-based DTS [6].
Category: