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:SA1 (blue squares, this study), SA2 (light blue diamonds, this study), SiO2 glass (red circles, Murakami and Bass 2010), and MgSiO3 glass (green triangles, Murakami and Bass 2011).
Category: