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:These include the SOM-based models such as WEBSOM (Kohonen et al., 2000) and LabelSOM (Rauber et al., 2000), the ART-based models such as ARTMAP (Carpenter et al., 1991a) and ARAM (Tan, 1995), as well as various hybrid models.
Category: