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. 2005, 2006, Derosier 2005), to enlighten contributing factors and root causes involved in…
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