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:Image segmentation techniques have been proposed from various perspectives, including clustering methods [94], region-growing methods [95], level set methods [96, 97], and a recently proposed inverse diffusion and expectation-maximization algorithm for materials images [98].
Category: