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:In particular, controllers for flying robots have taken inspiration from pheromone communication in ants (Hauert et al., 2008; Kuiper and Nadjm-Tehrani, 2006; Sauter et al., 2005), flocking by birds (Basu et al.
Category: