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 discretization is implemented within the DUNE numerics environment [3,4], centered around dune-gdt [23]: the dune-stuff [24] module provides classes for vectors, matrices and linear solvers (for instance the bicgstab.amg.ilu0 solver used in these experiments), dune-gdt provides the discretization building blocks (such as discrete function spaces, operators, products and functionals), and dune-hdd1 provides parametric discretizations compatible with pyMOR [22].
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