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:Sarbu [14] considered hyperintense fluid occurred more frequently and earlier in high-grade gliomas than in low-grade ones, which is something expected for a sign related to disease progression, given that high-grade gliomas progress earlier and more frequently than low-grade gliomas.
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