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:Nowadays, there are only a few studies that have a systemic view on these accidents (Bentley 2008) and which try, by using detailed analysis (Gao and Abeysekera 2004, Leclercq and Thouy 2004, Bentley et al.
Category: