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:Most patients diagnosed with NPC in Israel are found to have either nonkeratinizing carcinoma or undifferentiated carcinoma and are diagnosed at an advanced stage; both histology types are strongly associated with EBV [2, 3].
Category: