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:To minimize the contribution of each individual patient sample to the set of significantly altered genes [51] the statistical analysis has included a leave-one-out crossvalidation procedure; essentially, one sample was removed at a time, and every time a new set of significantly altered genes was determined using the remaining ten samples, ultimately pointing to the most consistently altered gene set, which is common to all leave-one-out sets (see Material and methods for details).
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