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:The inflection pressure of SA2 is 24 GPa lower than that of SiO2 glass (Murakami and Bass 2010) and 17 GPa lower than that of MgSiO3 glass (Murakami and Bass 2011).
Category: