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:Furthermore, considering that the 12.4 kb 3 enhancer expresses so uniformly in nearly all Ptf1a-expressing regions in the nervous
system, it is surprising that this element expresses very sparsely in the pancreas, and even then it is not active until much later in development (Masui et al., 2008).
Category: