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:…with 675 kHz scanning pencil beam sonar and a 200 kHz multibeam sonar for near-bottom bathymetric surveys, both with vertical resolution as high as centimeters to decimeters depending on acquisition parameters [Singh et al., 2000; Whitcomb et al., 2000; Roman et al., 2005; Ferrini et al., 2005b].
Category: