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:Partial or complete deletion of CS2, as in the case of ABF1 (1-643) and (1-638), doubled the plasmid loss rate of pARS1 (compare column 1 with columns 5 and 7 in Fig.
Category: