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:one stage of the life cycle may impact upon subsequent life history parameters (Post et al. 1997), whilst the inXuence of climate on multiple demographic parameters in the same species has rarely been studied in any taxon (Sillett et al.
Category: