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:…examined in section 2.2.4, there are many criteria upon which personalization can occur, like age groups, learning styles (Damala, 2007b), disabilities (Proctor, 2004), level of visitors initiation, available time for the visit (Damala et al., 2005), thematic tours, bookmarking, or social networks.
Category: