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:For this analysis we use the two SI distributions observed from investigations of the first 100 pH1N1 cases in South Africa [22]: (1) the SI distribution between primary cases and laboratoryconfirmed secondary cases only (39%, 24%, 14%, 17%, 3% and 3% for day 1 to 6 respectively), and (2) the SI distribution between primary cases and suspected plus laboratory-confirmed secondary cases (30%, 17%, 20%, 23%, 7% and 3% for day 1 to 6 respectively).
Category: