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:Others implicitly set γ ≡ 0 to investigate the relationship between damages and socioeconomic vulnerability; see Kellenberg and Mobarak (2008), Bakkensen (2013), Bakkensen and Mendelsohn (2016) and Geiger et al. (2016).
Category: