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:Occlusal wear facets were defined following Maier and Schneck (1981) and grouped using the dental occlusal compass concept (Douglass and DeVreugd, 1997; Ulhaas et al., 2007; Kullmer et al., 2009; see Fig.
Category: