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:By pooling the data sets from both Ouguerram et al [20] and Schwartz et al [21] and using mmap~2 to account for the difference in the structures of compartmental models, we obtain: kCETP HL
~5:47+2:05 pool/ day (mean6SEM).
Category: