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:…experiments and numerical analyses of stratified flow provide more tangible evidence that buoy-
ant gravity currents, characterized by a convergent front, can lead to accumulation and transport of buoyant particles in the direction of the propagating front (Franks 1997, Helfrich & Pineda 2003).
Category: