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 identify cell types by FCM, the target molecules of lineage-specific antibodies ideally should be (1) present on all the cells of that lineage, (2) uniquely expressed on that lineage, and (3) have known function.
Category: