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:Keros [14], later on, Kainz and Stammberger [26], described the cribriform plate variation and classified it into three types based on the length of the lateral lamella that determines the depth of the cribriform plate in the olfactory cleft.
Category: