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 genetic differentiation in PT is comparable to that observed in Castelvolturno (Spagnuolo et al. 2007), apart from a lower
number of haplotypes in the first than in the second (12/35 and 43/45, respectively).
Category: