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:Recent progresses have identified several novel surface markers, which can distinguish LSCs from normal HSCs, such as CD44 [15], CD123 [16], CLL-1 [17], TIM-1 [18], CD96 [19], CD47 [20].
Category: