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:…relative hazard functions characterized the instantaneous rate of death at a particular time, given that the individual survived up to that point, while controlling for the effect of other variables on survival (SPSS 1990;
Journal of Insect Science | www.insectscience.org 5
Rosengaus et al. 1998).
Category: