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:In a case series report of 13 patients with chronic pancreatitis who received IT therapy with morphine and/or other opioid or nonopioid medications via internal pump devices (40), meningitis was documented in two patients.
Category: