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:our approach did not include any cell preselection, neither positive, for CD34+ [8–11], nor negative, against CD3-CD14- [13], nor adherence depletion [1,3], and not even phased culturing [6,12,14]
Category: