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:This has already been shown to be the case in large genome-wide association studies in Alzheimer‚Äö√Ñ√¥s disease where several key genes involved in the innate immune system were shown to increase susceptibility to developing Alzheimer‚Äö√Ñ√¥s disease (Harold et al., 2009; Lambert et al., 2009; Guerreiro et al., 2013).
Category: