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:The impact of the human factors on the software industry and its projects is increasingly discussed and investigated in empirical studies (Hannay et al. 2010; Salleh et al. 2010b; Kosti et al. 2014; Lenberg et al. 2014).
Category: