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:Recent studies have shown that many pathogens, including Listeria monocytogenes and Yersinia pseudotuberculosis, utilize the ‘zippering’ pathway of invasion, highjacking the clathrin-, caveolin- and ubiquitin-mediated endocytosis of host receptors to gain access to the nutrient-rich intracellular environment of mammalian host cells (Veiga and Cossart, 2005; Bonazzi and Cossart, 2006; Hamon et al., 2006).
Category: